line 326 in builtin/describe.cdescribe.c, which is located in the function describe_commit. In the following code, cmit could be NULL passed to the call, which then causes a NULL dereference. Seems should be replaced lookup_commit_reference with lookup_commit_or_die.
```cpp
cmit = lookup_commit_reference(the_repository, oid);
n = find_commit_name(&cmit->object.oid);
```
The NULL value seems to come from function lookup_commit_reference_gently where:
- 1. call to deref_tag may return NULL.
- 2. call to object_as_type may return NULL.
In this repository, other calls lookup_commit_reference are followed by a null check. So this seems to lead to NULL dereference. Can I confirm with you whether this is a true positive bug report?
