Some serials removed after changes in r10900

Hi,

Seems serials coming from "entPhysicalSerialNum" is removed after changes in r10900.

I think maybe line 131 in /observium/trunk/includes/polling/os.inc.php

Relevant things from os debugging

Results:
[entPhysicalDescr] => string(24) "Dell Inc. PowerEdge R740"
[entPhysicalModelName] => string(14) "PowerEdge R740"
[entPhysicalSerialNum] => string(7) "60XXXV2"
[entPhysicalMfgName] => string(9) "Dell Inc."

Output:
Detected empty value for param 'serial'.
Added OS param from ENTITY-MIB: 'hardware' = 'PowerEdge R740'
Added OS param from ENTITY-MIB: 'vendor' = 'Dell Inc.'