Don't treat unknown lyrics fetchers as errors

src/settings.cpp

@@ -458,9 +458,24 @@ bool Configuration::read(const std::vector<std::string> &config_paths, bool igno
 	p.add("titles_visibility", &titles_visibility, "yes", yes_no);
 	p.add("header_text_scrolling", &header_text_scrolling, "yes", yes_no);
 	p.add("cyclic_scrolling", &use_cyclic_scrolling, "no", yes_no);
-	p.add("lyrics_fetchers", &lyrics_fetchers,
-	      "genius, tekstowo, plyrics, justsomelyrics, jahlyrics, zeneszoveg, internet",
-	      list_of<LyricsFetcher_>);
+	p.add<void>("lyrics_fetchers", nullptr,
+	      "genius, tekstowo, plyrics, justsomelyrics, jahlyrics, zeneszoveg, internet", [this](std::string v) {
+		      lyrics_fetchers = list_of<LyricsFetcher_>(v, [](std::string s) {
+			      LyricsFetcher_ fetcher;
+			      try {
+				      fetcher = boost::lexical_cast<LyricsFetcher_>(s);
+			      } catch (boost::bad_lexical_cast &) {
+				      std::clog << "Unknown lyrics fetcher: " << s << "\n";
+			      }
+			      return fetcher;
+		      });
+		      auto it = std::remove_if(
+			      lyrics_fetchers.begin(), lyrics_fetchers.end(),
+			      [](const auto &f) { return f.get() == nullptr; });
+		      lyrics_fetchers.resize(it - lyrics_fetchers.begin());
+		      if (lyrics_fetchers.empty())
+			      invalid_value(v);
+	      });
 	p.add("follow_now_playing_lyrics", &now_playing_lyrics, "no", yes_no);
 	p.add("fetch_lyrics_for_current_song_in_background", &fetch_lyrics_in_background,
 	      "no", yes_no);