[gnome-shell] keyboard: Fix widget leak

[Florian Müllner <fmuellner src gnome org>]

commit ff7dfa9259fc8f9f84705b6e87318a2cf39f2c80
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Dec 4 19:02:33 2019 +0100

    keyboard: Fix widget leak
    
    We currently create an extended-keys popup every time it is requested,
    but only destroy it (or rather: the last one) when the keyboard itself
    is destroyed.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/issues/1976

 js/ui/keyboard.js | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/js/ui/keyboard.js b/js/ui/keyboard.js
index a0483cc8a7..0d40c83572 100644
--- a/js/ui/keyboard.js
+++ b/js/ui/keyboard.js
@@ -292,6 +292,9 @@ var Key = GObject.registerClass({
         if (this._extendedKeys.length === 0)
             return;
 
+        if (this._boxPointer)
+            return;
+
         this._boxPointer = new BoxPointer.BoxPointer(St.Side.BOTTOM);
         this._boxPointer.hide();
         Main.layoutManager.addTopChrome(this._boxPointer);