[meld/ui-next] meldwindow: Handle stop action not existing on window close

[Kai Willadsen <kaiw src gnome org>]

commit 09b50a46ecb06e61d8b05bc52ee2b7f923f88089
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 13 08:49:51 2019 +1000

    meldwindow: Handle stop action not existing on window close

 meld/meldwindow.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/meld/meldwindow.py b/meld/meldwindow.py
index 02ee81fc..7f681e7a 100644
--- a/meld/meldwindow.py
+++ b/meld/meldwindow.py
@@ -182,7 +182,12 @@ class MeldWindow(Gtk.ApplicationWindow):
             self.spinner.hide()
             self.spinner.set_tooltip_text("")
             self.idle_hooked = None
-            self.lookup_action('stop').set_enabled(False)
+
+            # On window close, this idle loop races widget destruction,
+            # and so actions may already be gone at this point.
+            stop_action = self.lookup_action('stop')
+            if stop_action:
+                stop_action.set_enabled(False)
         return pending
 
     def on_scheduler_runnable(self, sched):