replace fail condition in selectcurrent with simple return

forced crashes as a result of this are infrequent and not reproducible to my knowledge

granted this condition should never occur, however i don't understand the practical necessity to force crash the game rather than just ignoring the command

it's possible there could be an issue not found when testing this and we can revisit this change if that is the case

Author: MinaciousGrace

src/ScreenSelectMusic.cpp

@@ -1223,7 +1223,10 @@ bool ScreenSelectMusic::SelectCurrent(PlayerNumber pn)
 
 	switch (m_SelectionState)
 	{
-		DEFAULT_FAIL(m_SelectionState);
+	case SelectionState_Finalized: {
+		LOG->Warn("song selection made while selectionstate_finalized");
+		return false;
+	}
 	case SelectionState_SelectingSong:
 		// If false, we don't have a selection just yet.
 		if (!m_MusicWheel.Select())

src/ScreenSelectMusic.h

@@ -117,7 +117,8 @@ class ScreenSelectMusic : public ScreenWithMenuElements
 			return TWO_PART_SELECTION ? SelectionState_SelectingSteps : SelectionState_Finalized;
 		case SelectionState_SelectingSteps:
 			return SelectionState_Finalized;
-		DEFAULT_FAIL( m_SelectionState );
+		case SelectionState_Finalized:
+			return SelectionState_Finalized;
 		}
 	}