pull up r22092 from trunk

pull up r22092 from trunk

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 r22092 | hartmans | 2009-03-16 12:49:59 -0400 (Mon, 16 Mar 2009) | 4 lines
 Changed paths:
    M /trunk/src/lib/krb5/krb/auth_con.c

 ticket: 6423
 Subject: krb5_auth_con_free should support freeing a null auth_context without segfault.

 If the input auth_con is NULL, return success.

ticket: 6423
version_fixed: 1.7

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-7@22226 dc483132-0cff-0310-8789-dd5450dbe970