Fix last change in xfaces.c

* src/xfaces.c (init_xfaces): Don't rely of 'face'
property of a face to be a natural number.
1 job for master in 60 minutes (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #668
test-all

01:00:00

 
Name Stage Failure
failed
test-all Test The script exceeded the maximum execution time set for the job
  GEN      lisp/eshell/eshell-tests.log
ELC lisp/faces-tests.elc
GEN lisp/faces-tests.log
ELC lisp/ffap-tests.elc
GEN lisp/ffap-tests.log
ELC lisp/filenotify-tests.elc
GEN lisp/filenotify-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-f100a208 ...
ERROR: Job failed: execution took longer than 1h0m0s seconds