67caab5f749ade98d973f42cc85b3b822f9ef9b7

If a change query uses reviewer information and loads the approvals map, but there are no approvals for a given patch set available, the collection came out null, which cannot be iterated. Make it always be an empty list. Change-Id: I5fd156a854099c5d4ce3c5c0c494b5498c4ed252
Description
RETIRED, Gerrit as used by OpenStack