Fix: tracks in custom parts no longer get muted when undoing instrument deletion

Author: RomanPudashkin

src/playback/internal/playbackcontroller.cpp

@@ -1286,7 +1286,11 @@ void PlaybackController::onTrackNewlyAdded(const InstrumentTrackId& instrumentTr
             if (notation == m_notation || notation->soloMuteState()->trackSoloMuteStateExists(instrumentTrackId)) {
                 continue;
             }
-            const INotationSoloMuteState::SoloMuteState soloMuteState = { /*mute*/ true, /*solo*/ false };
+
+            const Part* part = notation->parts()->part(instrumentTrackId.partId);
+            const bool shouldMute = !part || !part->show();
+
+            const INotationSoloMuteState::SoloMuteState soloMuteState = { shouldMute, /*solo*/ false };
             notation->soloMuteState()->setTrackSoloMuteState(instrumentTrackId, soloMuteState);
         }
     }