VSA multi-select project dropdown not allowing multi-select

Summary

In some scenarios, the multi-select project dropdown for VSA us not allowing multiple options to be selected.

Steps to reproduce

1. Use text search to find a project
2. Select that project
3. Use text search to find a different project
4. Select the project
5. The first selection is cleared

Example Project

In GitLab.org, this can be replicated by searching for "plan", selecting gitlab-org/Plan then searching for "security" and selecting gitlab-org/ce-security

What is the current bug behavior?

Initial selection is cleared

What is the expected correct behavior?

Initial selection is not cleared

Relevant logs and/or screenshots

Reported by a customer. Their video can be seen here (internal-only video)

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of: \`sudo gitlab-rake gitlab:env:info\`) (For installations from source run and paste the output of: \`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production\`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of: `sudo gitlab-rake gitlab:check SANITIZE=true`)

(For installations from source run and paste the output of: `sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`)

(we will only investigate if the tests are passing)

Possible fixes