typo

src/config.py

@@ -524,7 +524,7 @@ class PreferencesWindow:
 	def get_per_account_option(self, opt):
 		'''Return the value of the option opt if it's the same in all accounts
 		else returns "mixed"'''
-		if len(gajim.connections) = 0:
+		if len(gajim.connections) == 0:
 			# a non existant key return default value
 			return gajim.config.get_per('accounts', '__default__', opt)
 		val = None