Illegal division by 0

Great plugin!

When running the memory example however i get the following error:

15:34:18 /usr/local/icinga/libexec $ perl check_linux_stats.pl -M -w 90 -c 95
Illegal division by zero at check_linux_stats.pl line 250.

All the other checks, such as CPU, load, process vmem, network, io, etc work perfectly.

Thoughts?