-s/--schedule requires value

[Matthew James Kraai]

Hi,

When I run mcron 1.2.0 in Guix with -s or --schedule without a value, it 
displays the following error:

Backtrace:
           5 (primitive-load "/run/current-system/profile/bin/mcron")
In mcron/scripts/mcron.scm:
   113:12  4 (main)
In ice-9/getopt-long.scm:
    350:6  3 (getopt-long _ _ #:stop-at-first-non-option _)
In ice-9/boot-9.scm:
   260:13  2 (for-each #<procedure 7f65349b8ed0 at ice-9/getopt-lon…> …)
In ice-9/getopt-long.scm:
   209:28  1 (_ "schedule" _)
In unknown file:
           0 (string->number #t #<undefined>)

ERROR: In procedure string->number:
In procedure string->number: Wrong type argument in position 1 (expecting 
string): #t

This is inconsistent with the output of --help, which makes it seem like 
the value will default to 8:

  -s, --schedule[=N]         Display the next N (or 8) jobs that will be run

The info documentation makes it seem like the value is required:

'-s count'
'--schedule=count'

Should the value be required?

Matt