Crash in mod_md if httpd.json not readable

[Rainer Jung]

This is not new and of course mod_md can not work if md/httpd.json is 
not readable. But the process should not crash.

mod_md logs:
(13)Permission denied: AH10072: setup md registry

and then crashes.

In mod_md.c function md_post_config_before_ssl() we jump to leave after 
logging the message:

    886     rv = md_reg_create(&mc->reg, p, store, mc->proxy_url, 
mc->ca_certs,
    887                        mc->min_delay, mc->retry_failover,
    888                        mc->use_store_locks, mc->lock_wait_timeout);
    889     if (APR_SUCCESS != rv) {
    890         ap_log_error(APLOG_MARK, APLOG_ERR, rv, s, 
APLOGNO(10072) "setup md registry");
    891         goto leave;
    892     }

But in leave we have:

    947 leave:
    948     md_reg_unlock_global(mc->reg, ptemp);
    949     return rv;
    950 }

And this crashes in md_reg_unlock_global(), when mc->reg is NULL:

void md_reg_unlock_global(md_reg_t *reg, apr_pool_t *p)
{
    if (reg->use_store_locks) {
        md_store_unlock_global(reg->store, p);
    }
}

It might probably just be enough to check for NULL in leave.

Should I log an issue against GH mod_md?

Thanks and best regards,

Rainer