[FIX] account: avoid 0.0 tax lines

Don't create useless journal entries for taxes whose amount is 0.0.
Keep tax code lines creation unmodified.
Fixes #5036, opw 627055

addons/account/account_move_line.py

@@ -1374,6 +1374,8 @@ class account_move_line(osv.osv):
                     }
                     self.create(cr, uid, data, context)
                 #create the Tax movement
+                if not tax['amount']:
+                    continue
                 data = {
                     'move_id': vals['move_id'],
                     'name': tools.ustr(vals['name'] or '') + ' ' + tools.ustr(tax['name'] or ''),