parentEpic() JQL function should not be case-sensitive

Environment
JIRA Cloud

Steps to reproduce

1. Create an Epic ("DEMO-1")
2. Create a story in this epic ("DEMO-2")
3. Search for issues in DEMO-1 using the parentEpic JQL function, but reference the issuekey in lowercase, like parentEpic = demo-1

Expected behavior
JIRA will return DEMO-2 in the search results.

Actual behavior
JIRA returns a 500 error.