Steps to reproduce

1. Connect JIRA to an external user directory
2. Create a project and set Project Lead to one of the external users
3. Disable the external user directory, so that the Project Lead's user account is removed from JIRA
4. Go to Projects dropdown menu -> View All Projects and perform a project search

Expected behavior

Projects can be filtered using the keyword

Actual behaviors

1. The search function does not work and projects can't be filtered
2. The project with the external Project Lead states that it has no Project Lead:
   
3. The browser URL is not appended with &contains=<keyword>
4. The browser F12 Console shows this JS error:
   

Workaround

1. Find all the projects with the same problem from JIRA Administration -> Projects
2. Go to their Administration Panel -> Roles -> update Project Lead to an Active User
   

If there're too many projects to update, the following SQL query can be used to search for them in the database:

select * from project where lead not in (select lower_user_name from cwd_user);

Then the following query can be used to update the Project Lead of these projects to a valid username:

update project set lead = '<an_active_username_in_lowercase>' where lead not in (select lower_user_name from cwd_user);

the username must be in lowercase
JIRA needs restarting (and maybe re-indexing) for the change to take effect

Notes

1. Project Search always fails under All Projects category, because it definitely contains one or more problematic projects
2. Similarly, it fails under those Categories which contain one or more problematic projects
3. For those Categories without a problematic project, Project Filter works, no matter how many pages there are