QmlDesigner: Fix crash in property editor when parent of an item is invalid

Happened for

import Qt 4.6
Flipable {
  Rectangle {}
}

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/manual/qml/testfiles/flipable.qml b/tests/manual/qml/testfiles/flipable.qml
new file mode 100644
index 0000000000..16af9d7827
--- /dev/null
+++ b/tests/manual/qml/testfiles/flipable.qml
@@ -0,0 +1,6 @@
+import Qt 4.6
+
+Rectangle {
+    width: 640
+    height: 480
+}