PropertyExtractor: Add null check for event.submitter

If the change was open, it would cause event.submitter to be
null. Fix this by adding a null check.

Gerrit's core does the same thing.

Bug: Issue 8051
Change-Id: I0690e184ba50ea1e60176e8be5af34c43a80393e
1 file changed
tree: 1e5c8eb9189446bdf16cc5890efd3c0b60bf8b21
  1. .settings/
  2. src/
  3. tools/
  4. .gitignore
  5. bazlets.bzl
  6. BUILD
  7. LICENSE
  8. WORKSPACE