The JQL "watcher != user" and "watcher not in" are not working.

Summary

The JQL searches "watcher !=" and "watcher not in" are not working properly, they will return only issues where the watcher is not null, neither the referred user.

Steps to Reproduce

1. Create a new project (ex: TEST)
2. Create a new issue (ex: TEST-1)
3. Create two users, admin1 and admin2
4. Perform the JQL search: project = TEST and watcher != admin1, it will not return any issue.
5. Add admin2 as watcher in TEST-1.
6. Perform the JQL search: project = TEST and watcher != admin1, it will return the issue TEST-1.

Expected Results

The JQL "watcher != user" should returns issues where the watcher is not equals of user.

Actual Results

The JQL "watcher != user" only returns issues where the watcher is not equals of user and not null.