Make krb5_gss_accept_sec_context() check for a null authenticator
checksum pointer before attempting to dereference it.

https://github.com/krb5/krb5/commit/3d19e28dc97bb871cef0793e2cf4cf2a70aca239
Commit By: tlyu
Revision: 24056
Changed Files:
U   trunk/src/lib/gssapi/krb5/accept_sec_context.c