REST API breaks if an object deletion causes objects to not be consecutively numbered

To reproduce:

1. Add two objects of the same class to a page.
2. Use the REST API to get a list of all objects of that class on that page. I created two AppWithinMinutes.String objects on Main.WebHome, so I went to http://localhost:8080/xwiki/rest/wikis/xwiki/spaces/Main/pages/WebHome/objects/AppWithinMinutes.String
3. Delete the first object (object 0) from the page.
4. Retry step 2.

Expected result: An XML document that lists and describes the remaining object (object 1).

Actual result: 500 Internal Server Error

The same problem happens if you create three objects and then delete the one in the middle.