shell: Don't map surfaces of type SHELL_SURFACE_NONE

When commit 07926d90 factored out the code that chooses in which layer
a surface is added to, it changed the behavior for surfaces with no
type. Instead of not adding it to any layer, the surface is added to
the current workspace.

This patch restores the old behavior.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=77527

desktop-shell/shell.c

@@ -2127,6 +2127,12 @@ shell_surface_calculate_layer_link (struct shell_surface *shsurf)
 	struct weston_view *parent;
 
 	switch (shsurf->type) {
+	case SHELL_SURFACE_XWAYLAND:
+		return &shsurf->shell->fullscreen_layer.view_list;
+
+	case SHELL_SURFACE_NONE:
+		return NULL;
+
 	case SHELL_SURFACE_POPUP:
 	case SHELL_SURFACE_TOPLEVEL:
 		if (shsurf->state.fullscreen && !shsurf->state.lowered) {
@@ -2142,22 +2148,15 @@ shell_surface_calculate_layer_link (struct shell_surface *shsurf)
 			if (parent)
 				return parent->layer_link.prev;
 		}
-		break;
 
-	case SHELL_SURFACE_XWAYLAND:
-		return &shsurf->shell->fullscreen_layer.view_list;
-
-	case SHELL_SURFACE_NONE:
-	default:
-		/* Go to the fallback, below. */
-		break;
+		/* Move the surface to a normal workspace layer so that surfaces
+		 * which were previously fullscreen or transient are no longer
+		 * rendered on top. */
+		ws = get_current_workspace(shsurf->shell);
+		return &ws->layer.view_list;
 	}
 
-	/* Move the surface to a normal workspace layer so that surfaces
-	 * which were previously fullscreen or transient are no longer
-	 * rendered on top. */
-	ws = get_current_workspace(shsurf->shell);
-	return &ws->layer.view_list;
+	assert(0 && "Unknown shell surface type");
 }
 
 static void
@@ -2198,6 +2197,8 @@ shell_surface_update_layer(struct shell_surface *shsurf)
 
 	new_layer_link = shell_surface_calculate_layer_link(shsurf);
 
+	if (new_layer_link == NULL)
+		return;
 	if (new_layer_link == &shsurf->view->layer_link)
 		return;