Fix returnValue notification signal

src/grpc/quick/qquickgrpcsubscription.cpp

@@ -138,6 +138,8 @@ bool QQuickGrpcSubscription::subscribe()
     m_returnValue = reinterpret_cast<QObject*>(returnMetaType.create());
     qmlEngine(this)->setObjectOwnership(m_returnValue, QQmlEngine::CppOwnership);
 
+    returnValueChanged();
+
     if (m_returnValue == nullptr) {
         errorString = "Unable to allocate return value. Unknown metatype system error";
         qProtoWarning() << errorString;
@@ -145,8 +147,6 @@ bool QQuickGrpcSubscription::subscribe()
         return false;
     }
 
-    returnValueChanged();
-
     QGrpcSubscription *subscription = nullptr;
     bool ok = method.invoke(m_client, Qt::DirectConnection,
                                       QGenericReturnArgument("QtProtobuf::QGrpcSubscription*", static_cast<void *>(&subscription)),