fix: play next track correctly skips to queued track

src/playqueue.hpp

@@ -124,14 +124,17 @@ public:
         return static_cast<qint64>(current()["id"].toDouble());
     }
 
-    /// Advance and return the new current track.  Returns {} at end of queue.
+    /// Advance and return the track to play next.  Returns {} at end of queue.
     QJsonObject advance()
     {
         if (!m_playNext.isEmpty()) {
-            m_playNext.removeFirst();
+            // Return the playNext item directly — do NOT call current() after
-        } else {
+            // removal, as that would fall back to the already-playing m_index track.
-            ++m_index;
+            const QJsonObject next = m_playNext.takeFirst();
+            emit queueChanged();
+            return next;
         }
+        ++m_index;
         emit queueChanged();
         return current();
     }