Fix bug where calling TrackQueue's next() repeatedly would increase the position despite running off the end of the queue.

src/audio/track_queue.cpp

@@ -200,10 +200,13 @@ auto TrackQueue::next() -> void {
     shuffle_->next();
     pos_ = shuffle_->current();
   } else {
-    pos_++;
+    if (pos_ + 1 >= tracks_.size()) {
-    if (pos_ >= tracks_.size() && repeat_) {
+      if (repeat_) {
         pos_ = 0;
       }
+    } else {
+      pos_++;
+    }
   }
 
   notifyChanged(true);