SentTimeCache: fix new Coverity defects

This should fix defects 74787, 74788 and 74789 detected by the Coverity
scan on build 1466 on 2014-11-09. None of these defects are of any
importance, but fixing them seems to be the right thing to do.
Merge remote-tracking branch 'bertm/coverity-2014-11-09' into next