QmlDesigner.NodeInstances: Check expressions

I do not see any reason to set an expression that contains a
code block.

Change-Id: I74960a6bac741db46d86e33299e8b1669e781e65
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/objectnodeinstance.cpp

@@ -91,6 +91,14 @@ static bool isPropertyBlackListed(const QmlDesigner::PropertyName &propertyName)
     return false;
 }
 
+static bool isSimpleExpression(const QString &expression)
+{
+    if (expression.startsWith(QStringLiteral("{")))
+        return false;
+
+    return true;
+}
+
 namespace QmlDesigner {
 namespace Internal {
 
@@ -512,6 +520,9 @@ void ObjectNodeInstance::setPropertyBinding(const PropertyName &name, const QStr
     if (ignoredProperties().contains(name))
         return;
 
+    if (!isSimpleExpression(expression))
+        return;
+
     QQmlProperty property(object(), name, context());
 
     if (!property.isValid())