[ScreenSelectMaster] Add "ScreenEmpty" param to MenuStartP# when the GameCommand doesn't set a screen.

Docs/Changelog_sm5.txt

@@ -10,6 +10,8 @@ StepMania 5.0 $NEXT | 20110xyy
 
 2011/05/14
 ----------
+* [ScreenSelectMaster] Add "ScreenEmpty" param to MenuStartP# when the GameCommand
+  doesn't set a screen. [AJ]
 * [StepsDisplay] Added MeterFormatString metric. [AJ]
 * [MusicWheel] Added ShowSectionsInBPMSort and ShowSectionsInLengthSort metrics. [AJ]
 * [ScreenEvaluation] Stop the Bonus bars from overflowing in course modes. [AJ]

src/ScreenSelectMaster.cpp

@@ -812,8 +812,9 @@ void ScreenSelectMaster::MenuStart( const InputEventPlus &input )
 		mc.ApplyToAllPlayers();
 		// We want to be able to broadcast a Start message to the theme, in
 		// case a themer wants to handle something. -aj
-		// TODO: Add a param to differentiate this from the message below.
-		MESSAGEMAN->Broadcast( (MessageID)(Message_MenuStartP1+pn) );
+		Message msg( MessageIDToString((MessageID)(Message_MenuStartP1+pn)) );
+		msg.SetParam( "ScreenEmpty", true );
+		MESSAGEMAN->Broadcast( msg );
 		return;
 	}