Do not compare with $args->{fmt} if it is not initialized.
Quick temporary instructions for recent carton versions.

Carton started requiring a "cpanfile" file with requirements somewhere
between 0.9.4 and 0.9.10.
Merge branch 'mbs-5938' into beta

* mbs-5938:
  Do not compare with $args->{fmt} if it is not initialized.