Describe the bug

If you try and use a multiselect passing an array of class instances to the options property, internal filtering will not work, giving always an empty result set.

Pull Request Link

PR #17399

Reason for not contributing a PR

• Lack of time
• Unsure how to implement the fix/feature
• Difficulty understanding the codebase
• Other

Other Reason

Reproducer

https://stackblitz.com/edit/github-1ildik2r?file=src%2Fapp%2Fapp.component.html

Environment

**OS: ** Windows 11
**IDE: ** JetBrains Webstorm

Angular version

19.0.5

PrimeNG version

v19

Node version

22.9.0

Browser(s)

No response

Steps to reproduce the behavior

1. Create an array made of class instances
2. Use a <p-multi-select> and pass the array as [options]
3. Open MultiSelect's dropdown and try to filter the options
4. See error (filtered values is always empty)

Expected behavior

Since class instances are objects as well, it is expected by the filter to work as it does with plain objects