Changed GetFirstCompatibleStyle to not crash SM so it can be used to check whether joining is allowed. JoinPlayer and PlayersCanJoin now use GetFirstCompatibleStyle to check whether there will be a style to change to. Changed logic in PlayersCanJoin to return false at the first failed requirement.

src/ScreenSelectMusic.cpp

@@ -3,6 +3,7 @@
 #include "ScreenManager.h"
 #include "PrefsManager.h"
 #include "SongManager.h"
+#include "Game.h"
 #include "GameManager.h"
 #include "GameSoundManager.h"
 #include "GameConstantsAndTypes.h"
@@ -249,6 +250,13 @@ void ScreenSelectMusic::BeginScreen()
 		vector<StepsType> vst;
 		GAMEMAN->GetStepsTypesForGame( GAMESTATE->m_pCurGame, vst );
 		const Style *pStyle = GAMEMAN->GetFirstCompatibleStyle( GAMESTATE->m_pCurGame, GAMESTATE->GetNumSidesJoined(), vst[0] );
+		if(pStyle == NULL)
+		{
+			FAIL_M( ssprintf("No compatible styles for %s with %d player%s.",
+					GAMESTATE->m_pCurGame->m_szName,
+					GAMESTATE->GetNumSidesJoined(),
+					GAMESTATE->GetNumSidesJoined()==1?"":"s") );
+		}
 		GAMESTATE->SetCurrentStyle( pStyle, PLAYER_INVALID );
 	}