gtkplacesview: unset entry_pulse_timeout_id before removing it

Fixes a warning on widget finalize, when trying to remove an invalid
source.

gtk/gtkplacesview.c

@@ -1385,6 +1385,7 @@ pulse_entry_cb (gpointer user_data)
     {
       gtk_entry_set_progress_pulse_step (GTK_ENTRY (priv->address_entry), 0.0);
       gtk_entry_set_progress_fraction (GTK_ENTRY (priv->address_entry), 0.0);
+      priv->entry_pulse_timeout_id = 0;
 
       return G_SOURCE_REMOVE;
     }