windowManager: Disable favorite shortcuts without overview

The `switch-to-application-n` shortcuts are essentially "launch the nth
app in the dash" actions, so they are at the very least confusing when
the dash isn't available because the overview itself is disabled (for
example in initial-setup mode).

So disable the shortcuts when the overview is disabled, but delegate the
decision to a separate function so that extensions like 'panel-favorites'
which expose favorites by some other means can easily re-enable them.

https://gitlab.gnome.org/GNOME/gnome-shell/issues/1333

js/ui/windowManager.js

@@ -2121,7 +2121,14 @@ var WindowManager = class {
         Main.ctrlAltTabManager.popup(binding.is_reversed(), binding.get_name(), binding.get_mask());
     }
 
+    _allowFavoriteShortcuts() {
+        return Main.sessionMode.hasOverview;
+    }
+
     _switchToApplication(display, window, binding) {
+        if (!this._allowFavoriteShortcuts())
+            return;
+
         let [,,,target] = binding.get_name().split('-');
         let apps = AppFavorites.getAppFavorites().getFavorites();
         let app = apps[target - 1];