Installing the patched xul.dll file bricks Firefox

[xxHAKRxx]

So I downloaded the patched xul.dll file recommended for this theme, but when I replaced the existing file with the patched one and started Firefox, I was met with these errors:


Since I replaced the .dll file, I had basically bricked my browser and had to uninstall and reinstall Firefox to fix it. I later found out that the theme works fine without the patched file, but it won't affect the window buttons and some text is either white or completely invisible.
One thing I have noticed though is that the original xul.dll file is 135k KB, while the patched one was 128k KB. I dunno if that has to do with the patch bricking my browser, but it's just a guess.