Debug print out errors.

src/minimediaplayer.cpp

@@ -208,6 +208,7 @@ QList<QPair<QString,QUrl>> MiniMediaPlayer::getStreamTitlesAndUrlsFromUrl(QUrl m
         }
         else
         {
+            qDebug() << youtubedl.readAllStandardError();
             qWarning() << "Url may be invalid.";
         }
     }