Ensure enc_frm_finish() is called on error paths in oapve_encode()

[fkyslov]

Summary

Ensures enc_frm_finish() is called on error paths in oapve_encode() (src/oapv.c):

• Release input and reconstruction imgb reference counts via enc_frm_finish(ctx, stat) when enc_frame() or MD5 payload insertion returns an error after enc_frm_prepare().

Testing

• Verified all 24 ctest unit/conformance tests pass with AddressSanitizer and UndefinedBehaviorSanitizer.

[kpchoi]

The fix looks correct: enc_frm_prepare() takes the references at its end, and all three error paths between it and enc_frm_finish() now release them.

Two small refinements are suggested.

1. The mid == NULL check is an argument check, so it can be done at the top of oapve_encode(), before any frame is prepared. Then no cleanup is needed for it:

    for(i = 0; i < ifrms->num_frms; i++) {
        frm = &ifrms->frm[i];
        if(ctx->use_frm_hash[i] &&
           (frm->pbu_type == OAPV_PBU_TYPE_PRIMARY_FRAME || frm->pbu_type == OAPV_PBU_TYPE_NON_PRIMARY_FRAME)) {
            oapv_assert_rv(mid != NULL, OAPV_ERR_INVALID_ARGUMENT);
        }
    }

2. The remaining two error paths can use the oapv_assert_gv() / ERR: pattern that is used elsewhere in this file, instead of repeating enc_frm_finish() and return:

        ret = enc_frame(ctx, bs);
        oapv_assert_gv(OAPV_SUCCEEDED(ret), ret, ret, ERR);
        ...
        if(ctx->use_frm_hash[i]) {
            if(frm->pbu_type == OAPV_PBU_TYPE_PRIMARY_FRAME ||
               frm->pbu_type == OAPV_PBU_TYPE_NON_PRIMARY_FRAME) {
                ret = oapv_set_md5_pld(mid, frm->group_id, ctx->imgb_r);
                oapv_assert_gv(OAPV_SUCCEEDED(ret), ret, ret, ERR);
            }
        }
    ...
    return OAPV_OK;

ERR:
    enc_frm_finish(ctx, stat);
    return ret;
}

ERR: is reached only from inside the frame loop, after enc_frm_prepare() has succeeded, so enc_frm_finish() always releases exactly the references taken for the current frame.

[fkyslov]

Updated per review feedback: moved the mid != NULL validation when ctx->use_frm_hash[i] is enabled before enc_frm_prepare(), and routed post-prepare error paths to an ERR: label that calls enc_frm_finish(ctx, stat).

[kpchoi]

LGTM

[kpchoi]

LGTM