QbsProjectManager: Delete ProjectDocuments along with project

The documents have a reload callback that accesses the project. This
would lead to a crash on a reload for a document belonging to a closed
project.

Change-Id: I171cacd0da347fb279609baaea4050ba1cc12008
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/qbsprojectmanager/qbsproject.cpp

@@ -158,6 +158,8 @@ QbsProject::~QbsProject()
         m_qbsUpdateFutureInterface = 0;
     }
     qDeleteAll(m_extraCompilers);
+    std::for_each(m_qbsDocuments.cbegin(), m_qbsDocuments.cend(),
+                  [](Core::IDocument *doc) { doc->deleteLater(); });
 }
 
 QbsRootProjectNode *QbsProject::rootProjectNode() const