don't bother parsing for empty commands

stepmania/src/ActorCommands.cpp

@@ -58,6 +58,12 @@ void ActorCommands::PushSelf( lua_State *L ) const
 
 void ActorCommands::Register( const Commands& cmds )
 {
+	if( cmds.v.size() == 0 )
+	{
+		m_sLuaFunctionName = "nop";
+		return;
+	}
+
 	// TODO: calculate a better function name, or figure out how
 	// to keep a pointer directly to the Lua function so no global
 	// table lookup is necessary.
@@ -130,9 +136,12 @@ void ActorCommands::Unregister()
 
 	ASSERT( m_sLuaFunctionName.size() );
 
+	if( m_sLuaFunctionName != "nop" )
+	{
 		lua_pushstring( LUA->L, m_sLuaFunctionName );
 		lua_pushnil( LUA->L );
 		lua_settable( LUA->L, LUA_GLOBALSINDEX );
+	}
 
 	m_sLuaFunctionName = "";
 }

stepmania/src/LuaManager.cpp

@@ -184,6 +184,8 @@ void LuaManager::ResetState()
 	luaopen_string( L );
 	lua_settop(L, 0); // luaopen_* pushes stuff onto the stack that we don't need
 
+	RunScript( "nop = function(self) end" );
+
 	for( const LuaFunctionList *p = g_LuaFunctions; p; p=p->next )
 		lua_register( L, p->name, p->func );