rem: while(_s->first) {
add: while ((_s->first) && (_s->n > 0)) {
context: void deinit_slot(hslot_t* _s){	presentity_t* ptr;		     /* Remove all elements */	while(_s->first) {		ptr = _s->first;		_s->first = _s->first->next;		free_presentity(ptr);	}		_s->n = 0;        _s->d = 0;}