Qmake: Deactivate parse guard before it can cause trouble

... in the QmakeBuildSystem destructor

Change-Id: I23336cc0b72673fd2c63235b1c568439159d3d8d
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/qmakeprojectmanager/qmakebuildconfiguration.cpp

@@ -249,9 +249,11 @@ void QmakeBuildConfiguration::updateProblemLabel()
     }
 
     const auto bs = qmakeBuildSystem();
-    if (bs->rootProFile()->parseInProgress() || !bs->rootProFile()->validParse()) {
-        buildDirectoryAspect()->setProblem({});
-        return;
+    if (QmakeProFile *rootProFile = bs->rootProFile()) {
+        if (rootProFile->parseInProgress() || !rootProFile->validParse()) {
+            buildDirectoryAspect()->setProblem({});
+            return;
+        }
     }
 
     bool targetMismatch = false;

src/plugins/qmakeprojectmanager/qmakeproject.cpp

@@ -231,6 +231,7 @@ QmakeBuildSystem::QmakeBuildSystem(QmakeBuildConfiguration *bc)
 
 QmakeBuildSystem::~QmakeBuildSystem()
 {
+    m_guard = {};
     delete m_cppCodeModelUpdater;
     m_cppCodeModelUpdater = nullptr;
     m_asyncUpdateState = ShuttingDown;