Send cancel IQ if muc configuration is aborted

Fixes #9069

gajim/common/connection.py

@@ -2720,6 +2720,17 @@ class Connection(CommonConnection, ConnectionHandlers):
         self.add_lang(iq)
         self.connection.send(iq)
 
+    def cancel_gc_config(self, room_jid):
+        if not app.account_is_connected(self.name):
+            return
+        cancel = nbxmpp.Node(tag='x', attrs={'xmlns': nbxmpp.NS_DATA,
+                                             'type': 'cancel'})
+        iq = nbxmpp.Iq(typ='set',
+                       queryNS=nbxmpp.NS_MUC_OWNER,
+                       payload=cancel,
+                       to=room_jid)
+        self.connection.send(iq)
+
     def destroy_gc_room(self, room_jid, reason = '', jid = ''):
         if not app.account_is_connected(self.name):
             return

gajim/config.py

@@ -1642,9 +1642,12 @@ class GroupchatConfigWindow:
                 affiliation)
 
         self.xml.connect_signals(self)
+        self.window.connect('delete-event', self.on_cancel_button_clicked)
         self.window.show_all()
 
-    def on_cancel_button_clicked(self, widget):
+    def on_cancel_button_clicked(self, *args):
+        if self.form:
+            app.connections[self.account].cancel_gc_config(self.room_jid)
         self.window.destroy()
 
     def on_cell_edited(self, cell, path, new_text):