Fix Bugs Discovered by Steve

[jameskerr]

1. Fix presentation of null record types.
2. Properly abort queries.
3. Provide shallow copies of objects in the collect callback.

Details

We were not catching the abort error properly when issuing a query before the previous query finished.

We also were not aborting all of the histogram queries when re-issuing a search.

This stuff is really hard to write tests for. There are no tests in this PR. 🤷‍♂️

To test this, re-issue the search with a large pool over and over again rapidly. Open the network tab and view all the in-flight requests properly cancelling when a new search is issued.

Fixes #2997
Fixes #2999
Fixes #2838

[philrz]

I spent some time circling back to reproduce the original symptoms and captured those in #2997 and #2999, then tested this branch at commit 668f78d and the problems do indeed seem to be fixed. Therefore I'm 👍 on this.