EditTagDialog: Add button to fetch lyrics

Co-Authored-By: Jonas Kvinge <jonas@jkvinge.net>

src/lyrics/lyricsfetchersearch.cpp

@@ -134,6 +134,9 @@ void LyricsFetcherSearch::AllProvidersFinished() {
     qLog(Debug) << "Using lyrics from" << results_.last().provider << "for" << request_.artist << request_.title << "with score" << results_.last().score;
     emit LyricsFetched(id_, results_.last().provider, results_.last().lyrics);
   }
+  else {
+    emit LyricsFetched(id_, QString(), QString());
+  }
 
   emit SearchFinished(id_, results_);