fix: critical, fixed list_empty not actually freeing the allocated list

leading to orphanned memory

list.c

@@ -37,8 +37,8 @@ List list_copy(const List* source) {
 }
 
 void list_empty(List* self) {
-    if(self->data == NULL || self->cap == 0)
-        return;
+    if(self->data != NULL && self->cap != 0)
+        free(self->data);
     self->data = NULL;
     self->cap = 0;
     self->len = 0;