{
if(direction)
{
- if( list->marker->next!=NULL)
+ if( list->marker && list->marker->next!=NULL)
list->marker=list->marker->next;
else
return(NULL);
}
else
{
- if( list->marker->prev!=NULL)
+ if( list->marker && list->marker->prev!=NULL)
list->marker=list->marker->prev;
else
return(NULL);