Core: Use FilePath for working dir in MainWindow::openFiles()

Change-Id: Ifc8e167a1734115fa7a23f7aefa45fc52e4a70cc
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/coreplugin.cpp

@@ -309,7 +309,7 @@ QObject *CorePlugin::remoteCommand(const QStringList & /* options */,
     IDocument *res = MainWindow::openFiles(
                 filePaths,
                 ICore::OpenFilesFlags(ICore::SwitchMode | ICore::CanContainLineAndColumnNumbers | ICore::SwitchSplitIfAlreadyVisible),
-                workingDirectory);
+                FilePath::fromString(workingDirectory));
     m_mainWindow->raiseWindow();
     return res;
 }