Fix unassigned checkmark

What does this MR do?

• Fixes regression with selecting Unassigned in the Assignee dropdown when filtering Issuables

Are there points in the code the reviewer needs to double check?

Make sure there are no unwanted side effects

Why was this MR needed?

Fixes regression

Screenshots (if relevant)

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #31843 (closed)

added 1 commit

• 17caba91 - Fix unassigned checkmark

Compare with previous version

added 122 commits

• 17caba91...cae08033 - 120 commits from branch master
• ee2db2c1 - Fix unassigned checkmark
• 37a76e8e - Fix eslint

Compare with previous version

added 1 commit

• 70f4aaae - Add spec

Compare with previous version

added ~149423 frontend labels

changed milestone to %9.2

assigned to @iamphill

mentioned in merge request !11147 (closed)

Just the one question @ClemMakesApps I understand though that the GL dropdown is a bit of a mess

assigned to @ClemMakesApps

added 57 commits

• 70f4aaae...0bc2fef9 - 54 commits from branch master
• 72b7e48d - Fix unassigned checkmark
• 8fc68b68 - Fix eslint
• 0654955f - Add spec

Compare with previous version

Once this is ready to go, I'll create the ee MR

assigned to @iamphill

resolved all discussions

approved this merge request

merged

mentioned in commit 2242a2d7

added regression label

mentioned in commit f12d7db1

mentioned in merge request !11528 (merged)

@ClemMakesApps: This MR doesn't apply cleanly onto 9-2-stable. Could you please fix the conflicts in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11528?