QbsBuildSystem: Don't delete an object from its signal handler

Delete it later instead.

Change-Id: Iff0b0d2410752f324f0fea15c0314b60fd637b5e
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qbsprojectmanager/qbsproject.cpp

@@ -561,7 +561,7 @@ void QbsBuildSystem::handleQbsParsingDone(bool success)
         m_qbsUpdateFutureInterface->reportCanceled();
     }
 
-    delete m_qbsProjectParser;
+    m_qbsProjectParser->deleteLater();
     m_qbsProjectParser = nullptr;
     m_qbsUpdateFutureInterface->reportFinished();
     delete m_qbsUpdateFutureInterface;