The reputation_change field is missing from the reputation results on some CW posts

Question

When querying the /users/{ids}/reputation API route, the reputation_change field is missing from the results on community-wiki answers. I think the reputation type should always include this field, and its value should be 0 if there was no reputation change on the post. (Alternatively, you could just exclude 0-change reputation objects from the query results.)

Here's a query example with results that are missing the reputation_change field:

https://api.stackexchange.com/docs/reputation-on-users#page=8&pagesize=100&ids=1288&filter=default&site=stackoverflow&run=true

The CW posts 13977422 and 13975947 are the two that are missing the field.

{
  "on_date": 1356103151,
  "vote_type": "accepts",
  "post_type": "answer",
  "post_id": 13977422,
  "user_id": 1288
},
{
  "on_date": 1356060056,
  "vote_type": "accepts",
  "post_type": "answer",
  "post_id": 13975947,
  "user_id": 1288
}

The two examples above are answer accepts, but this also sometimes happens on answer upvotes.

{
  "on_date": 1379667908,
  "vote_type": "up_votes",
  "post_type": "answer",
  "post_id": 8669380,
  "user_id": 1288
}

{
  "on_date": 1374767790,
  "vote_type": "up_votes",
  "post_type": "answer",
  "post_id": 17593979,
  "user_id": 1288
}

But not always. Here's one that has a reputation_change value of 0.

{
  "on_date": 1380379795,
  "reputation_change": 0,
  "vote_type": "up_votes",
  "post_type": "answer",
  "post_id": 623007,
  "user_id": 1288
}

From this very small sample, it looks like the reputation_change field is missing on posts where the community wiki checkbox was checked when the post was created.