[omemo] Dont handle type 'normal' messages

omemo/omemoplugin.py

@@ -589,6 +589,9 @@ class OmemoPlugin(GajimPlugin):
             -------
             Return if encryption is not activated
         """
+        if event.type_ == 'normal':
+            return False
+
         account = event.account
         if account in self.disabled_accounts:
             return