Sort nulls last in data tables

[lbeaufort]

Summary (required)

• Follow-up front-end task for Add ability to sort nulls last openFEC#3470 and Resolves Inconsistency between information displayed on data page and download file #2481

Because we can't know where null values belong, we should always sort nulls last (at the bottom, on the last pages) in data tables.

Impacted areas of the application, how to test

List general components of the application that this PR will affect:

• Point to dev API

• Check datatables (below is not a list of all the datatables, but a list of tables that were showing nulls on first load). They should all show nulls at the end.

  • IEs - http://localhost:8000/data/independent-expenditures/?data_type=processed&is_notice=true
  • Party coordinated - http://localhost:8000/data/party-coordinated-expenditures/
  • Loans - http://localhost:8000/data/loans/
  • Candidates - http://localhost:8000/data/candidates/?has_raised_funds=true
  • Committees - http://localhost:8000/data/committees/
  • RFAIs - http://localhost:8000/data/filings/?data_type=processed&form_type=RFAI
  • All filings - http://localhost:8000/data/filings/?data_type=processed
  • House and Senate committee reports - http://localhost:8000/data/reports/house-senate/?data_type=processed

[lbeaufort]

@johnnyporkchops the API change has been merged, so this is ready when you have a chance. Thank you!

[johnnyporkchops]

Tested locally and works as expected