quick_frontend: keep the contact list groups synchronised on contact deletion

frontends/src/quick_frontend/quick_contact_list.py

@@ -208,6 +208,7 @@ class QuickContactList(QuickWidget):
         @param name: name of the data (can't be "jids")
         @param value: value to set
         """
+        # FIXME: this is never used, should it be removed?
         assert name is not 'jids'
         self._groups[group][name] = value
 
@@ -368,6 +369,8 @@ class QuickContactList(QuickWidget):
         del self._cache[entity_bare]
         for group in groups:
             self._groups[group]['jids'].remove(entity_bare)
+            if not self._groups[group]['jids']:
+                self._groups.pop(group)
         for set_ in (self._selected, self._alerts, self._specials, self._special_extras):
             to_remove = set()
             for set_entity in set_: