Do not close chat window on ESC key when roster filtering is active

When the roster window active it can be filtered by starting to type.
If the window behavior "single window for everything" is selected,
trying to abort the filtering by pressing the ESC key also closes a chat
window. Fix this behavior by stopping event propagation in case the ESC
key is pressed while roster filtering is active.

Fixes issue #8548.

src/roster_window.py

@@ -3805,7 +3805,7 @@ class RosterWindow:
         if event.keyval == Gdk.KEY_Escape:
             if self.rfilter_enabled:
                 self.disable_rfilter()
-                return
+                return True
             if gajim.interface.msg_win_mgr.mode == \
             MessageWindowMgr.ONE_MSG_WINDOW_ALWAYS_WITH_ROSTER and \
             gajim.interface.msg_win_mgr.one_window_opened():