runAsyncWithProgress cannot target an UI element with no parent, wi…

…ll no throw Exception with warning (#873)

CHANGELOG.md

@@ -7,6 +7,7 @@
 - `config` no longer accepts null values, as the underlying `Properties` store won't allow them (https://github.com/edvin/tornadofx/issues/792). The set function that takes Pair still accepts null as the value, but will remove the key if the value is null.
 - the `di()` delegate no longer calls out to the `DIContainer` for every access, effectively caching the lookup (https://github.com/edvin/tornadofx/issues/837)
 - More efficient timer for delayed `runLater` calls (https://github.com/edvin/tornadofx/pull/836)
+- `runAsyncWithProgress` cannot target an UI element with no parent, will no throw Exception with warning (https://github.com/edvin/tornadofx/issues/873)
 
 ### Changes
 

src/main/java/tornadofx/Async.kt

@@ -257,7 +257,7 @@ fun <T : Any> Node.runAsyncWithProgress(progress: Node = ProgressIndicator(), op
         val paddingVertical = (this as? Region)?.paddingVertical?.toDouble() ?: 0.0
         (progress as? Region)?.setPrefSize(boundsInParent.width - paddingHorizontal, boundsInParent.height - paddingVertical)
         // Unwrap ToolBar parent, it has an extra HBox or VBox inside it, we need to target the items list
-        val p = (parent?.parent as? ToolBar) ?: parent
+        val p = (parent?.parent as? ToolBar) ?: parent ?: throw IllegalArgumentException("runAsyncWithProgress cannot target an UI element with no parent!")
         val children = requireNotNull(p.getChildList()) { "This node has no child list, and cannot contain the progress node" }
         val index = children.indexOf(this)
         children.add(index, progress)