Fix Metal Archives possibly returning 'lyrics not available'

Fixes #323

src/main.cpp

@@ -42,6 +42,7 @@ void OpenLyricsVersion::get_about_message(pfc::string_base & out)
     "  - If a source returns only one type you'll get that type regardless\n"
     "- Fix the lyric editor sometimes responding badly to Ctrl-A/Ctrl-Backspace\n"
     "- Fix possibly using the wrong background colour when changing FB2K colours\n"
+    "- Fix Metal Archives possibly returning 'lyrics not available'\n"
     "- Many, many minor non-functional internal code improvements\n"
     "\n";
     out += "Version 1.9 (2024-06-12):\n"

src/sources/metalarchives.cpp

@@ -245,6 +245,10 @@ bool MetalArchivesSource::lookup(LyricDataRaw& data, abort_callback& abort)
     const pugi::xml_document lyric_doc = load_html(content.c_str());
     const std::string lyric_text = collect_all_text_to_string(lyric_doc);
 
+    if(lyric_text == "(lyrics not available)") {
+        return false;
+    }
+
     data.text_bytes = string_to_raw_bytes(lyric_text);
     data.source_path = std::move(url);
     return !data.text_bytes.empty();