app: set the idle_id to 0 in gimp_image_profile_view_query()

fixes warnings from dispose() about removing a source that doesn't
exist.

app/widgets/gimpimageprofileview.c

@@ -185,6 +185,8 @@ gimp_image_profile_view_query (GimpImageProfileView *view)
   g_free (desc);
   g_free (info);
 
+  view->idle_id = 0;
+
   return FALSE;
 }