fix ScreenSelect loading screens two or three times (!) due to broken

"clear m_sScreen" logic

stepmania/src/GameCommand.cpp

@@ -608,6 +608,29 @@ static HighScore MakeRandomHighScore( float fPercentDP )
 	return hs;
 }
 
+/* Hack: if this GameCommand would set the screen, clear the setting and return
+ * the screen that would have been set. */
+CString GameCommand::GetAndClearScreen()
+{
+	CString sRet;
+	FOREACH( Command, m_Commands.v, cmd )
+	{
+		GameCommand gc;
+		gc.m_bInvalid = false;
+		gc.LoadOne( *cmd );
+		if( gc.m_sScreen != "" )
+		{
+			sRet = gc.m_sScreen;
+			m_Commands.v.erase( cmd );
+			break;
+		}
+	}
+
+	m_sScreen = "";
+
+	return sRet;
+}
+
 void GameCommand::Apply( const vector<PlayerNumber> &vpns ) const
 {
 	if( m_Commands.v.size() )

stepmania/src/GameCommand.h

@@ -37,6 +37,7 @@ public:
 	bool DescribesCurrentModeForAllPlayers() const;
 	bool IsPlayable( CString *why = NULL ) const;
 	bool IsZero() const;
+	CString GetAndClearScreen();
 
 	// Same as what was passed to Load.  We need to keep the original commands
 	// so that we know the order of commands when it comes time to Apply.

stepmania/src/ScreenSelect.cpp

@@ -212,9 +212,9 @@ void ScreenSelect::HandleScreenMessage( const ScreenMessage SM )
 		FOREACH_HumanPlayer( p )
 		{
 			GameCommand gc = m_aGameCommands[this->GetSelectionIndex(p)];
+			CString sThisScreen = gc.GetAndClearScreen();
 			if( sScreen == "" )
-				sScreen = gc.m_sScreen;
-			gc.m_sScreen = "";
+				sScreen = sThisScreen;
 			gc.Apply( p );
 		}