And if rc != 0 ?
Because, below, you test (env != 0) as precondition of calling mdb_env_close(env), even if rc was non-zero here; if mdb_env_create(&env) != 0 can leave env uninitialized, then you'll call mdb_env_close(uninitialized) when that happens.
If in doubt, initialize env, where it's declared, to 0.