[gnome-shell] layout: Check again for primary monitor after startup animation idle

[Marge Bot <marge-bot src gnome org>]

commit 85b51b9974e253e90ced85cd77090eb0b6d33d02
Author: 13r0ck <bnr tuta io>
Date:   Tue Feb 1 13:04:19 2022 -0700

    layout: Check again for primary monitor after startup animation idle
    
    On some hardware combinations the display can be known, then unknown again. Meaining that
    when the update monitors function is called it will have a value, then be called again
    setting this.primaryMonitor to null. If the timing is just right gnome shell will
    loadBackground, then by the time the animation is ready the monitor will be gone,
    thus methods will be called on a null value. This adds more checks for a valid
    primary monitor, and wont play the animation until the system is idle AND has a valid
    priamry monitor.
    
    Fixes: #5003
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2144>

 js/ui/layout.js | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
---
diff --git a/js/ui/layout.js b/js/ui/layout.js
index e629f62807..0f279f86c8 100644
--- a/js/ui/layout.js
+++ b/js/ui/layout.js
@@ -650,10 +650,14 @@ var LayoutManager = GObject.registerClass({
             // This helps to prevent us from running the animation
             // when the system is bogged down
             const id = GLib.idle_add(GLib.PRIORITY_LOW, () => {
-                this._systemBackground.show();
-                global.stage.show();
-                this._prepareStartupAnimation();
-                return GLib.SOURCE_REMOVE;
+                if (this.primaryMonitor) {
+                    this._systemBackground.show();
+                    global.stage.show();
+                    this._prepareStartupAnimation();
+                    return GLib.SOURCE_REMOVE;
+                } else {
+                    return GLib.SOURCE_CONTINUE;
+                }
             });
             GLib.Source.set_name_by_id(id, '[gnome-shell] Startup Animation');
         });