[gnome-shell] status/keyboard: Check for monkey-patched property before using it

[verdre <jonasd src gnome org>]

commit ee6635282c4cd03421758477e8998b86fd58970c
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Feb 20 16:03:54 2020 +0100

    status/keyboard: Check for monkey-patched property before using it
    
    This avoid another "reference to undefined property" warning.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/1035

 js/ui/status/keyboard.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/js/ui/status/keyboard.js b/js/ui/status/keyboard.js
index 2f0ab94f05..b2e16bc485 100644
--- a/js/ui/status/keyboard.js
+++ b/js/ui/status/keyboard.js
@@ -715,7 +715,8 @@ var InputSourceManager = class {
         if (!window)
             return;
 
-        if (window._inputSources != this._inputSources) {
+        if (!window._inputSources ||
+            window._inputSources !== this._inputSources) {
             window._inputSources = this._inputSources;
             window._currentSource = this._getNewInputSource(window._currentSource);
         }