frontends: dialog don't crash anymore is no submit_id is given (submit does nothing in this case)

frontends/src/tools/xmlui.py

@@ -161,7 +161,10 @@ class Dialog(object):
         self._xmluiClose()
 
     def _xmluiSubmit(self, data):
-        self._xmlui_parent.submit(data)
+        if self._xmlui_parent.submit_id is None:
+            log.debug(_("Nothing to submit"))
+        else:
+            self._xmlui_parent.submit(data)
 
     def _xmluiSetData(self, status, data):
         pass