avoid warning when model has no “object”

For example, 996935.xml:

      <oidobject>
         <object></object>
         <oid>.1.3.6.1.2.1.2.1.0</oid>
         <portcounter>1</portcounter>
         <dynamicport>0</dynamicport>
         <vlan>0</vlan>
         <activation>1</activation>
      </oidobject>
ensure result value exists

this to avoid a odd number of element in the hash table.
use Carp::Always::Color