Numeric based NIDs can have address "0". This causes problems for nid_addr_is_set() which can only look for a non-zero address value.
This causes two bugs:

• If a node has multiple NIDs on one net, one of the NIDs has a 0
  address, then an attempt to delete the 0 address NID will cause
  all NIDs on the network to be removed.
• If the source NID specified for lnetctl ping has a 0 address then
  this is not correctly passed down to the kernel (so the ping is
  processed as though no souce NID were specified).