allow a scroll time of 0 for non-scrolling lists

stepmania/src/ActorScroller.cpp

@@ -27,7 +27,6 @@ void ActorScroller::Load(
 	const RageVector3	&vTranslateTerm2
 	)
 {
-	ASSERT( fSecondsPerItem > 0 );
 	m_fSecondsPerItem = fSecondsPerItem;
 	m_iNumItemsToDraw = iNumItemsToDraw;
 	m_vRotationDegrees = vRotationDegrees;
@@ -45,7 +44,8 @@ void ActorScroller::Update( float fDeltaTime )
 	if( m_fHibernateSecondsLeft > 0 )
 		return;	// early abort
 
-	fapproach( m_fCurrentItem, m_fDestinationItem, fDeltaTime/m_fSecondsPerItem );
+	if( m_fSecondsPerItem > 0 )
+		fapproach( m_fCurrentItem, m_fDestinationItem, fDeltaTime/m_fSecondsPerItem );
 }
 
 void ActorScroller::DrawPrimitives()

stepmania/src/ActorScroller.h

@@ -29,7 +29,7 @@ protected:
 	bool		m_bLoaded;
 	float		m_fCurrentItem; // usually between 0 and m_SubActors.size()
 	float		m_fDestinationItem;
-	float		m_fSecondsPerItem;
+	float		m_fSecondsPerItem;		// <= 0 means don't scroll
 	int			m_iNumItemsToDraw;
 	
 	// Note: Rotation is applied before translation.