Fix crash when playing Pattern Editor without Pattern Track (#7862)

Fixes a crash that occurs when attempting to play within the Pattern Editor with no Pattern Track created.

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Co-authored-by: Sotonye Atemie <sakertooth@gmail.com>

src/core/Song.cpp

@@ -366,7 +366,7 @@ void Song::processAutomations(const TrackList &tracklist, TimePos timeStart, fpp
 		break;
 	case PlayMode::Pattern:
 	{
-		Q_ASSERT(tracklist.size() == 1);
+		if (tracklist.empty()) { return; }
 		Q_ASSERT(tracklist.at(0)->type() == Track::Type::Pattern);
 		auto patternTrack = dynamic_cast<PatternTrack*>(tracklist.at(0));
 		container = Engine::patternStore();