[FIX] account: default value for report_vat report

If the report was printed from the tax codes list
Accounting > Configuration > Taxes > Tax codes
There is no information concerning what should be displayed (periods, details, etc.)
as the user did not printed the report from the wizard
(from Accounting > Reporting > Generic Reporting > Taxes > Taxes report)
We therefore set default values, in order the report to not crash

Nevertheless, the user has obviously to go through the wizard
if he wants to set a configuration different than the default one

addons/account/report/report_vat.py

@@ -31,6 +31,15 @@ class tax_report(report_sxw.rml_parse, common_report_header):
     def set_context(self, objects, data, ids, report_type=None):
         new_ids = ids
         res = {}
+        if not data:
+            company_id = self.pool['res.users'].browse(self.cr, self.uid, self.uid).company_id.id
+            data = {
+                'form': {
+                    'based_on': 'invoices',
+                    'company_id': company_id,
+                    'display_detail': False,
+                }
+            }
         self.period_ids = []
         period_obj = self.pool.get('account.period')
         self.display_detail = data['form']['display_detail']