don't count finished thread as "running" in cache manager

musicdb-lib/src/data/song.rs

@@ -88,7 +88,7 @@ impl Song {
         let mut cd = self.cached_data.0.lock().unwrap();
         match cd.0.as_ref() {
             None => (),
-            Some(Err(_)) => return Err(true),
+            Some(Err(t)) => return Err(!t.is_finished()),
             Some(Ok(_)) => return Err(false),
         };
         let src = if let Some(dlcon) = &db.remote_server_as_song_file_source {