Fix list slice

src/list/copy.c

@@ -169,17 +169,14 @@ size_t list_slice(list_t* x, list_t* s, ssize_t i, size_t n, _Bool cut) {
     } else {
         if (c->prev) {
             c->prev->next = e->next;
-        } else x->first = e->next;
+        } else s->first = e->next;
 
         if (e->next) {
             e->next->prev = c->prev;
         } else s->last = c->prev;
 
-        e->next = nullptr;
-        c->prev = nullptr;
-
-        x->first = c;
-        x->last  = e;
+        (x->first = c)->prev = nullptr;
+        (x->last  = e)->next = nullptr;
     }
 
     return r;