Fix editor crash if you don't save a new chart.

Docs/Changelog_sm5.txt

@@ -15,6 +15,8 @@ StepMania 5.0 Preview 2 | 201106??
   than one step in all stepstypes. This needs testing. [Wolfman2000]
 * [ScreenEdit] Add the option to convert delays to beats. Just find a better
   song to use this on besides Uprock. [Wolfman2000]
+* [ScreenEdit] Fix a crash if you don't save any steps on a new song.
+  [Wolfman2000]
 
 2011/06/19
 ----------

src/Player.cpp

@@ -960,8 +960,10 @@ void Player::Update( float fDeltaTime )
 	UpdateJudgedRows();
 
 	// Check for TapNote misses
-	UpdateTapNotesMissedOlderThan( GetMaxStepDistanceSeconds() );
-
+	if (!GAMESTATE->m_bInStepEditor)
+	{
+		UpdateTapNotesMissedOlderThan( GetMaxStepDistanceSeconds() );
+	}
 	// process transforms that are waiting to be applied
 	ApplyWaitingTransforms();
 }