CompilationDbProjectManager: Fix tree scanning

- We checked for the QFuture's canceled status at a time where it would
  always yield true.
- A pointless default value was used for the project root path.

Fixes: QTCREATORBUG-26356
Change-Id: I4d17c6ecb7e9e7e71df737d85b42feb37d3ead5d
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.cpp

@@ -437,17 +437,14 @@ CompilationDatabaseProject::CompilationDatabaseProject(const Utils::FilePath &pr
 
 Utils::FilePath CompilationDatabaseProject::rootPathFromSettings() const
 {
-#ifdef WITH_TESTS
-    return Utils::FilePath::fromString(projectDirectory().fileName());
-#else
-    auto rootPath = Utils::FilePath::fromString(
+    Utils::FilePath rootPath;
+#ifndef WITH_TESTS
+    rootPath = Utils::FilePath::fromString(
         namedSettings(ProjectExplorer::Constants::PROJECT_ROOT_PATH_KEY).toString());
-
-    if (rootPath.isEmpty())
-        rootPath = Utils::FilePath::fromString(projectDirectory().fileName());
-
-    return rootPath;
 #endif
+    if (rootPath.isEmpty())
+        rootPath = projectDirectory();
+    return rootPath;
 }
 
 void CompilationDatabaseProject::configureAsExampleProject(Kit *kit)

src/plugins/compilationdatabaseprojectmanager/compilationdbparser.cpp

@@ -138,9 +138,9 @@ void CompilationDbParser::stop()
 
 QList<FileNode *> CompilationDbParser::scannedFiles() const
 {
+    const bool canceled = m_treeScanner->future().isCanceled();
     const TreeScanner::Result result = m_treeScanner->release();
-    return m_treeScanner && !m_treeScanner->future().isCanceled() ? result.allFiles
-                                                                  : QList<FileNode *>();
+    return !canceled ? result.allFiles : QList<FileNode *>();
 }
 
 void CompilationDbParser::parserJobFinished()