Fix Implicitly Unwrapped Optional Crash

The presentationController variable is declared as an implicitly unwrapped optional (line 38):

private var presentationController: SideMenuPresentationController!

There are situations where this will cause a crash, as the property could be null while transitioning:

Crashed: com.apple.main-thread
0  MyApp                          0x102c57398 closure jonkykong#1 in SideMenuNavigationController.viewWillTransition(to:with:) + 107 (SideMenuAnimationController.swift:107)
1  MyApp                          0x102c573d0 thunk for @escaping @callee_guaranteed (@guaranteed UIViewControllerTransitionCoordinatorContext) -> () + 4336055248 (<compiler-generated>:4336055248)
2  UIKitCore                      0x1b67c58f4 -[_UIViewControllerTransitionCoordinator _applyBlocks:releaseBlocks:] + 276
3  UIKitCore                      0x1b67c21b4 -[_UIViewControllerTransitionContext __runAlongsideAnimations] + 284
4  UIKitCore                      0x1b67d9b38 -[_UIWindowAnimationController animateTransition:] + 344
5  UIKitCore                      0x1b6e48044 -[UIWindow _adjustSizeClassesAndResizeWindowToFrame:] + 964
6  UIKitCore                      0x1b6e546b4 -[UIWindow _resizeWindowFrameToSceneBoundsIfNecessary] + 252
7  UIKitCore                      0x1b6e4a26c __78-[UIWindow _rotateWindowToOrientation:updateStatusBar:duration:skipCallbacks:]_block_invoke + 408
8  UIKitCore                      0x1b67da1e8 __58-[_UIWindowRotationAnimationController animateTransition:]_block_invoke_2 + 180
9  UIKitCore                      0x1b72d0e48 +[UIView(Internal) _performBlockDelayingTriggeringResponderEvents:forScene:] + 212
10 UIKitCore                      0x1b67d9fd4 __58-[_UIWindowRotationAnimationController animateTransition:]_block_invoke + 180
11 UIKitCore                      0x1b67d9e98 -[_UIWindowRotationAnimationController animateTransition:] + 524
12 UIKitCore                      0x1b6e478c4 -[UIWindow _rotateToBounds:withAnimator:transitionContext:] + 624
13 UIKitCore                      0x1b6e49f74 -[UIWindow _rotateWindowToOrientation:updateStatusBar:duration:skipCallbacks:] + 1436
14 UIKitCore                      0x1b6e4a4b0 -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:] + 404
15 UIKitCore                      0x1b6e49844 -[UIWindow _setRotatableViewOrientation:updateStatusBar:duration:force:] + 132
16 UIKitCore                      0x1b66bf2dc -[_UIFullscreenPresentationController _placeCounterRotationViewWithView:inWindow:fromOrientation:toOrientation:force:] + 520
17 UIKitCore                      0x1b66bf010 -[_UIFullscreenPresentationController _adjustOrientationIfNecessaryInWindow:forViewController:preservingViewController:] + 908
18 UIKitCore                      0x1b66b45ec -[UIPresentationController _presentWithAnimationController:interactionController:target:didEndSelector:] + 900
19 UIKitCore                      0x1b67a8590 -[UIViewController _presentViewController:modalSourceViewController:presentationController:animationController:interactionController:completion:] + 1416
20 UIKitCore                      0x1b67a9f74 -[UIViewController _presentViewController:withAnimationController:completion:] + 4212
21 UIKitCore                      0x1b67ac540 __63-[UIViewController _presentViewController:animated:completion:]_block_invoke + 108
22 UIKitCore                      0x1b67aca94 -[UIViewController _performCoordinatedPresentOrDismiss:animated:] + 528
23 UIKitCore                      0x1b67ac48c -[UIViewController _presentViewController:animated:completion:] + 212
24 UIKitCore                      0x1b67ac720 -[UIViewController presentViewController:animated:completion:] + 176
25 UIKitCore                      0x1b6f6f9b8 __74-[UIStoryboardPresentationSegueTemplate newDefaultPerformHandlerForSegue:]_block_invoke + 148
26 UIKitCore                      0x1b6f75a18 -[UIStoryboardSegueTemplate _performWithDestinationViewController:sender:] + 296
27 UIKitCore                      0x1b6f758bc -[UIStoryboardSegueTemplate _perform:] + 96
28 UIKitCore                      0x1b6f75b98 -[UIStoryboardSegueTemplate perform:] + 164
29 UIKitCore                      0x1b6e086c0 -[UIApplication sendAction:to:from:forEvent:] + 100
30 UIKitCore                      0x1b6479858 __45-[_UIButtonBarTargetAction _invoke:forEvent:]_block_invoke + 84
31 UIKitCore                      0x1b64796e4 -[_UIButtonBarTargetAction _invoke:forEvent:] + 256
32 UIKitCore                      0x1b6e086c0 -[UIApplication sendAction:to:from:forEvent:] + 100
33 UIKitCore                      0x1b67f0b30 -[UIControl sendAction:to:forEvent:] + 208
34 UIKitCore                      0x1b67f0e98 -[UIControl _sendActionsForEvents:withEvent:] + 400
35 UIKitCore                      0x1b67efeb0 -[UIControl touchesEnded:withEvent:] + 520
36 UIKitCore                      0x1b6e43b08 -[UIWindow _sendTouchesForEvent:] + 1024
37 UIKitCore                      0x1b6e452f0 -[UIWindow sendEvent:] + 3548
38 UIKitCore                      0x1b6e2045c -[UIApplication sendEvent:] + 348
39 UIKitCore                      0x1b6ea3a54 __dispatchPreprocessedEventFromEventQueue + 6688
40 UIKitCore                      0x1b6ea6648 __handleEventQueueInternal + 5368
41 UIKitCore                      0x1b6e9e578 __handleHIDEventFetcherDrain + 144
42 CoreFoundation                 0x1b2c39af4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28
43 CoreFoundation                 0x1b2c39a48 __CFRunLoopDoSource0 + 84
44 CoreFoundation                 0x1b2c39198 __CFRunLoopDoSources0 + 196
45 CoreFoundation                 0x1b2c33f38 __CFRunLoopRun + 796
46 CoreFoundation                 0x1b2c338f4 CFRunLoopRunSpecific + 480
47 GraphicsServices               0x1bd04a604 GSEventRunModal + 164
48 UIKitCore                      0x1b6e07358 UIApplicationMain + 1944
49 MyApp                          0x102921628 main + 15 (AppDelegate.swift:15)
50 libdyld.dylib                  0x1b2aaf2dc start + 4

By making it a normal optional, we can avoid such crashes.

Pod/Classes/SideMenuAnimationController.swift

@@ -35,7 +35,7 @@ internal final class SideMenuAnimationController: NSObject, UIViewControllerAnim
     private weak var containerView: UIView?
     private let leftSide: Bool
     private weak var originalSuperview: UIView?
-    private var presentationController: SideMenuPresentationController!
+    private var presentationController: SideMenuPresentationController?
     private unowned var presentedViewController: UIViewController?
     private unowned var presentingViewController: UIViewController?
     weak var delegate: SideMenuAnimationControllerDelegate?
@@ -104,7 +104,7 @@ internal final class SideMenuAnimationController: NSObject, UIViewControllerAnim
     }
 
     func layout() {
-        presentationController.containerViewWillLayoutSubviews()
+        presentationController?.containerViewWillLayoutSubviews()
     }
 }
 
@@ -131,25 +131,25 @@ private extension SideMenuAnimationController {
         // prevent any other menu gestures from firing
         containerView?.isUserInteractionEnabled = false
         if presenting {
-            presentationController.presentationTransitionWillBegin()
+            presentationController?.presentationTransitionWillBegin()
         } else {
-            presentationController.dismissalTransitionWillBegin()
+            presentationController?.dismissalTransitionWillBegin()
         }
     }
 
     func transition(presenting: Bool) {
         if presenting {
-            presentationController.presentationTransition()
+            presentationController?.presentationTransition()
         } else {
-            presentationController.dismissalTransition()
+            presentationController?.dismissalTransition()
         }
     }
 
     func transitionDidEnd(presenting: Bool, completed: Bool) {
         if presenting {
-            presentationController.presentationTransitionDidEnd(completed)
+            presentationController?.presentationTransitionDidEnd(completed)
         } else {
-            presentationController.dismissalTransitionDidEnd(completed)
+            presentationController?.dismissalTransitionDidEnd(completed)
         }
         containerView?.isUserInteractionEnabled = true
     }