Fix gnome shell problems with lock screen

- Credits to @NikMel in this [issue](projecthamster#295 (comment))

extension/extension.js

@@ -21,7 +21,6 @@ Copyright (c) 2016 - 2018 Eric Goller / projecthamster <elbenfreund@projecthamst
 */
 
 
-const GLib = imports.gi.GLib;
 const Lang = imports.lang;
 const Shell = imports.gi.Shell;
 const Meta = imports.gi.Meta;
@@ -82,7 +81,7 @@ const WindowsProxyIface = ['',
 
 let WindowsProxy = Gio.DBusProxy.makeProxyWrapper(WindowsProxyIface);
 
-
+var isKeyBindingActive = 0; // Toggle whether keybinding is registered (attempt to fix crashing problems with Main.wm.RemoveKeyBinding in disable:)
 
 
 /**
@@ -184,17 +183,21 @@ function Controller(extensionMeta) {
                 Shell.KeyBindingMode ? Shell.KeyBindingMode.ALL : Shell.ActionMode.ALL,
                 Lang.bind(this.panelWidget, this.panelWidget.toggle)
             );
+            this.isKeyBindingActive = 1;
         },
 
         disable: function() {
             this.shouldEnable = false;
-            Main.wm.removeKeybinding("show-hamster-dropdown");
 
+            if(this.isKeyBindingActive == 1) {
+                global.log('Removing keybinding.');
+                Main.wm.removeKeybinding("show-hamster-dropdown");
+            } else {
+                global.log('(!!) Skipped removing keybinding as it was not enabled... Probably avoided a crash!');
+            }
+            this.isKeyBindingActive = 0;
             global.log('Shutting down hamster-shell-extension.');
             this._removeWidget(this.placement);
-            Main.panel.menuManager.removeMenu(this.panelWidget.menu);
-            GLib.source_remove(this.panelWidget.timeout);
-            this.panelWidget.actor.destroy();
             this.panelWidget.destroy();
             this.panelWidget = null;
             this.apiProxy = null;