When reuse key is enabled and the context has already been used, the code intended to call HMAC_Init_ex with a null key to reuse the existing key. An unconditional second HMAC_Init_ex call always re-passed the key, overwriting that path.

Use an else branch so only one initialization runs, matching the reuse semantics and aligning with similar crypto context lifecycle fixes (e.g. SERVER-119317 for MD5 hash state).