Bug 6895" Avoid "Use of uninitialized value" warnings in DKIM plugin on broken signatures - one more

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/trunk@1437595 13f79535-47bb-0310-9956-ffa450edef68
(adding a comment)

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/trunk@1437596 13f79535-47bb-0310-9956-ffa450edef68