Use null instead of "N/A" as default change-number

Missing change.id is more clear to the consumer than interpreting a
string when change-number isn't available.

Solves: Jira GER-1698
Change-Id: Ic801fe799ba53d363306c443cb3e92993452ef65
2 files changed
tree: 753302b27ee2836f31958cc58b92031fe5b3773b
  1. src/
  2. BUILD
  3. external_plugin_deps.bzl