Guard the .meta creation in openMetaFile against the directory watcher

openMetaFile creates the .meta file via QSettings when one does not
exist; the disk write fires directoryChanged and triggers a spurious
refreshList. Wrap it in a DirWatcherManager::Guard like the other
meta-file editing paths.

src/downloadmanager.cpp

@@ -1278,6 +1278,7 @@ void DownloadManager::openMetaFile(int index)
     shell::Open(metaPath);
     return;
   } else {
+    DirWatcherManager::Guard dirWatcherGuard = m_DirWatcher.scopedGuard();
     QSettings metaFile(metaPath, QSettings::IniFormat);
     metaFile.setValue("removed", false);
   }