check_uptime.pl perfdata empty when uptime has 0 hours

[danielferrer]

Example:
$ uptime
11:55:38 up 189 days, 20 min, 3 users, load average: 0.06, 0.08, 0.04

$ ./check_uptime.pl
OK: Linux mysystem.domain.com 2.6.32-358.18.1.el6.x86_64 - up 11:55:38 up 189 days, 20 min, 3 users, load average: 0.06, 0.08, 0.04 | type=1

So no uptime_mins= in perf data