Various Plugins: Simplify return FilePath statements

Change-Id: Ia9efb86f722caca1492b577d51442f1f23b804b4
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/utils/filepath.cpp

@@ -985,12 +985,12 @@ FilePath FilePath::parentDir() const
 {
     const QString basePath = path();
     if (basePath.isEmpty())
-        return FilePath();
+        return {};
 
     const QString path = basePath + QLatin1String("/..");
     const QString parent = doCleanPath(path);
     if (parent == path)
-        return FilePath();
+        return {};
 
     return withNewPath(parent);
 }