ro_community cannot be set to 'undef' to remove from ERB template

[bdellegrazie]

Hi,

Presently in the snmpd.conf ERB template, ro_community and the others are all tested for 'nil' value before outputting the content - this is fine. However the way the parameters are constructed with the ENC backend and the hard coded default there is no possible way to set the variable to undef and consequently skip its output.

Can I suggest checking for both nil and size > 0 as this would allow forcefully disabling the output of those parameters?

I will issue a pull request since it is just a template change.