The code in WT-6673 was reverted several days ago. Part of that code change was a bug fix to an assertion. Now that the code is reverted, some people are seeing the assertion segfault dereferencing a null pointer. The assertion is in txn_recover.c:

        WT_ASSERT(session,
          conn->recovery_ckpt_snapshot_count == counter &&
            conn->recovery_ckpt_snapshot[0] == conn->recovery_ckpt_snap_min &&
            conn->recovery_ckpt_snapshot[counter - 1] < conn->recovery_ckpt_snap_max);

We are unconditionally dereferencing recovery_ckpt_snapshot but conditionally allocate it.