shellcore: skip surface recovery while only a placeholder screen exists

related #3057

quickshell/ShellCore.qml

@@ -236,6 +236,10 @@ Item {
     }
 
     function refreshScreenSurfaces() {
+        if (!_hasRealScreen()) {
+            log.info("Surface refresh skipped: no real screen");
+            return;
+        }
         log.info("Refreshing layer surfaces, screens:", Quickshell.screens.length, Quickshell.screens.map(s => s.name).join(","));
         SurfaceRecovery.refreshAll();
         surfaceRefreshVerifyTimer.restart();
@@ -289,6 +293,14 @@ Item {
         repeat: false
         property int pass: 0
         onTriggered: {
+            // Rebuilding against a placeholder-only screen list feeds a dangling screen to the per-screen delegate models and segfaults (#3057); onScreensChanged reschedules once outputs return.
+            if (!root._hasRealScreen()) {
+                log.info("Surface recovery skipped: no real screen");
+                pass = 0;
+                interval = 800;
+                return;
+            }
+
             pass++;
             log.info("Surface recovery pass", pass, "screens:", Quickshell.screens.length, Quickshell.screens.map(s => s.name).join(","));