Fix async song load

Fixes #739

src/core/song.cpp

@@ -367,6 +367,7 @@ bool Song::save_embedded_cover_supported(const FileType filetype) {
 const QUrl &Song::stream_url() const { return d->stream_url_; }
 const QUrl &Song::effective_stream_url() const { return !d->stream_url_.isEmpty() && d->stream_url_.isValid() ? d->stream_url_ : d->url_; }
 const QImage &Song::image() const { return d->image_; }
+bool Song::init_from_file() const { return d->init_from_file_; }
 
 const QString &Song::cue_path() const { return d->cue_path_; }
 bool Song::has_cue() const { return !d->cue_path_.isEmpty(); }

src/core/song.h

@@ -294,6 +294,7 @@ class Song {
   const QUrl &stream_url() const;
   const QUrl &effective_stream_url() const;
   const QImage &image() const;
+  bool init_from_file() const;
 
   // Pretty accessors
   QString PrettyTitle() const;

src/core/songloader.cpp

@@ -339,7 +339,7 @@ void SongLoader::EffectiveSongLoad(Song *song) {
 
   if (!song) return;
 
-  if (song->filetype() != Song::FileType_Unknown) {
+  if (song->init_from_file() && song->filetype() != Song::FileType_Unknown) {
     // Maybe we loaded the metadata already, for example from a cuesheet.
     return;
   }