Perl warnings after 2.7.0 upgrade

[Michael Orlitzky]

Probably harmless, but I racked up about 450 of these overnight after
the upgrade to 2.7.0:

  Jul  4 09:20:26 mx1 amavis[26145]: (26145-08) _WARN: Argument "x"
  isn't numeric in sprintf at /usr/sbin/amavisd line 13126, <GEN11>
  line 390.