Annotate methods that return a definitely null value with @Nullable

We intend to enable the ReturnMissingNullable errorprone pattern in
Gerrit core and this fixes the current issues.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I53a642afe69214799324f572c8d8737abc88c986
1 file changed
tree: 3a0ba81e007f15fa7ef2ef508a99408ed4c406c2
  1. src/
  2. BUILD
  3. LICENSE