heimdal: Fix NULL deref
A flawed logical condition allows a malicious actor to remotely
trigger a NULL pointer dereference using a crafted negTokenInit
token.
Upstream notes:
Reported to Heimdal by Michał Kępień <michal@isc.org>. From the report: Acknowledgement --------------- This flaw was found while working on addressing ZDI-CAN-12302: ISC BIND TKEY Query Heap-based Buffer Overflow Remote Code Execution Vulnerability, which was reported to ISC by Trend Micro's Zero Day
Security: CVE-2022-3116
Obtained from: upstream 7a19658c1
MFC after: 1 week