Make sure to send playlist length if zero or send detected length.

src/minimediaplayer.cpp

@@ -119,7 +119,11 @@ QMap<QString, qint64> MiniMediaPlayer::currentState()
 
 void MiniMediaPlayer::durationChanged(qint64 length)
 {
-    //emit trackDurationChanged(length); //Don't emit duration changed since we already have duration. TODO: might want to use this still if implement another media source besides youtube-dl.
+    if(length == 0) {
+        emit trackDurationChanged(playlist.first().trackLength);
+    } else {
+        emit trackDurationChanged(length);
+    }
 }
 
 void MiniMediaPlayer::positionChanged(qint64 position)