[krbdev.mit.edu #8666] KDC null dereference when TGS reply is too big for UDP

[Greg Hudson via RT]

Using a test case, I verified that prior to 
0a2f14f752c32a24200363cc6b6ae64a92f81379, the KDC successfully responds 
to a TGS request with a too-big error if the reply length exceeds 
max_dgram_reply_size, and after that commit the KDC seg faults with a 
null dereference.