Fix task output warning background color

AB#335

src/@batch-flask/ui/loading/loading.scss

@@ -89,7 +89,7 @@ bl-loading {
 .entity-not-found {
     width: 600px;
     margin: 50px auto;
-    background: $warn-color-light;
+    background: $warn-color;
     padding: 10px;
     color: $warn-contrast-color;
     white-space: pre;