won't fix anything but for the sake of correctness

lab01/zad3/src/doubly_linked_list.c

@@ -7,6 +7,7 @@ Node *node_new(void *value, size_t element_size) {
     Node *new = (Node*)malloc(sizeof(Node));
     new->value = memcpy(malloc(element_size), value, sizeof(element_size));
     new->next = NULL;
+    new->prev = NULL;
 
     return new;
 }