[gnome-shell] messageTray: Add missing property getter

[verdre <jonasd src gnome org>]

commit 5e254666b0ad459b480dca454788ca0d0003ba8c
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Apr 30 00:43:32 2020 +0200

    messageTray: Add missing property getter
    
    gjs has gotten less forgiving about missing getters/setters, and
    commit 6aa1b817 missed the missing getter in the base policy class.
    
    Most notifications use a policy subclass that already provides a
    getter, but at least Main.notify() and friends don't; unbreak them
    by fixing the base class.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1229

 js/ui/messageTray.js | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/js/ui/messageTray.js b/js/ui/messageTray.js
index dc5ed9ce16..058f1ef912 100644
--- a/js/ui/messageTray.js
+++ b/js/ui/messageTray.js
@@ -162,6 +162,10 @@ var NotificationPolicy = GObject.registerClass({
         this.run_dispose();
     }
 
+    get enable() {
+        return true;
+    }
+
     get enableSound() {
         return true;
     }