fix(multiselect): prevent crash with virtualScroller when many items selected

[navedqb]

Fixes #8355

[github-actions]

Thanks a lot for your contribution! But, PR does not seem to be linked to any issues. Please manually link to an issue or mention it in the description using #<issue_id>.

[Coderxrohan]

Issue
MultiSelect could crash or become unstable when used with VirtualScroller and a large number of selected values due to costly lookup logic and unconditional scrolling.

Fix
Optimizes option lookup by switching to a Set-based approach when selection size is large and adds defensive checks around VirtualScroller.scrollToIndex, limiting auto-scroll when many items are selected.

Impact
Improves stability and performance for large selections while preserving existing behavior for smaller datasets.

⭐ Rating: 4.5/5

[Coderxrohan]

Hey @navedqb,
Thanks for the fix 👍
CI is failing for two reasons:

1. first, there’s an ESLint error in components/lib/multiselect/MultiSelect.js (around line ~774) where a blank line is required by the padding-line-between-statements rule;
2. second, the PR is not properly linked to an issue. Please add the missing blank line and update the PR title, description, or commit message to reference the issue (e.g. Fixes MultiSelect: virtualScrollerOptions #8355 or Fixed MultiSelect: virtualScrollerOptions #8355). Once these are addressed, the checks should pass and I’ll re-review again.
   I liked the approach you used.

Thanks!