Replace unsafe unwrap() calls in character conversion functions #7434

Problem Description

In several character conversion functions in , there are unsafe calls that can cause panics when handling invalid Unicode characters.

Specifically, these functions use :

• :
• :
• :
• :

These calls can panic if:

1. fails (invalid Unicode codepoint)
2. or returns (empty iterator)

Expected Behavior

These functions should handle invalid inputs gracefully by returning appropriate default values instead of panicking.

Proposed Solution

Replace with safer alternatives like or proper error handling. For example:

• For case conversion: fall back to the original character if conversion fails
• For character property checks: return for invalid characters

This would make the code more robust and prevent unexpected crashes when processing malformed or edge-case Unicode input.