Fixed a crash on exit when include files are still being scanned

Found by Roberto.

src/plugins/cpptools/cppmodelmanager.cpp

@@ -727,7 +727,7 @@ QByteArray CppModelManager::internalDefinedMacros() const
     return macros;
 }
 
-void CppModelManager::setIncludesInPaths(const QMap<QString, QStringList> includesInPaths)
+void CppModelManager::setIncludesInPaths(const QMap<QString, QStringList> &includesInPaths)
 {
     QMutexLocker locker(&mutex);
     QMapIterator<QString, QStringList> i(includesInPaths);
@@ -1182,7 +1182,7 @@ void CppModelManager::updateIncludesInPaths(QFutureInterface<void> &future,
             future.waitForResume();
 
         if (future.isCanceled())
-            break;
+            return;
 
         const QString path = paths.takeFirst();
 

src/plugins/cpptools/cppmodelmanager.h

@@ -163,7 +163,7 @@ private:
     QStringList internalFrameworkPaths() const;
     QByteArray internalDefinedMacros() const;
 
-    void setIncludesInPaths(const QMap<QString, QStringList> includesInPaths);
+    void setIncludesInPaths(const QMap<QString, QStringList> &includesInPaths);
 
     static void updateIncludesInPaths(QFutureInterface<void> &future,
                                       CppModelManager *manager,