workspace: Check if index is valid before using it

If the window wasn't in _windowSlots, the index is -1, so the last
element of the array is removed, leading to
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3547

I logged the stack trace from removeWindow() and it seems that when you
move the window from the second monitor to another workspace like shown
in https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3547,
removeWindow() is called twice for it, presumably once for the second
monitor workspace, and then once for the first monitor workspace for
some reason. It is during that call that _windowSlots doesn't contain
the window, so instead the last element (index -1) is removed, leading
to the animation bug.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1727>

diff --git a/js/ui/workspace.js b/js/ui/workspace.js
index a21b5b43ca46deca4641352d8a8632e0d304c1ad..4fa113bac363f662fb2b0264c70a5f15b3621caf 100644 (file)
--- a/js/ui/workspace.js
+++ b/js/ui/workspace.js
@@ -784,8 +784,9 @@ var WorkspaceLayout = GObject.registerClass({
 
         // The layout might be frozen and we might not update the windowSlots
         // on the next allocation, so remove the slot now already
-        this._windowSlots.splice(
-            this._windowSlots.findIndex(s => s[4] === window), 1);
+        const index = this._windowSlots.findIndex(s => s[4] === window);
+        if (index !== -1)
+            this._windowSlots.splice(index, 1);
 
         // The window might have been reparented by DND
         if (window.get_parent() === this._container)