Any scroller that has an OnCommand for its parts may want to PositionItems

first, not just ScreenSelectMaster's.  Also, the position set by this depends
on SetNumSubdivisions, which (will be) set by OnCommand, and not set this
early.  So, use PositionItems manually if wanted.

stepmania/src/ScreenSelectMaster.cpp

@@ -239,15 +239,6 @@ void ScreenSelectMaster::BeginScreen()
 			vpns.push_back( p );
 	}
 
-	// position scroller items so that the items will start from their resting 
-	// position when they execute their OnCommand.
-	if( SHOW_SCROLLER )
-	{
-		FOREACH( PlayerNumber, vpns, p )
-			m_Scroller[*p].PositionItems();
-	}
-
-
 	this->UpdateSelectableChoices();
 
 	ScreenSelect::BeginScreen();
@@ -255,7 +246,6 @@ void ScreenSelectMaster::BeginScreen()
 	m_fLockInputSecs = (bool)OVERRIDE_LOCK_INPUT_SECONDS ? LOCK_INPUT_SECONDS : this->GetTweenTimeLeft();
 	if( m_fLockInputSecs == 0 )
 		m_fLockInputSecs = 0.0001f;	// always lock for a tiny amount of time so that we throw away any queued inputs during the load.
-
 }
 
 void ScreenSelectMaster::Update( float fDelta )