Unstyled DatePicker throws error onKeyDown if input field is empty

[mikahozz]

Describe the bug

When opening the calendar and clicking an arrow down, DatePicker throws an error:

TypeError: Cannot read properties of undefined (reading 'focus')
    at Proxy.trapFocus (primevue_datepicker.js?v=ecbf9ced:4352:46)
    at Proxy.onKeyDown (primevue_datepicker.js?v=ecbf9ced:4407:14)
    at callWithErrorHandling (chunk-YYVLN2RI.js?v=ecbf9ced:1678:19)
    at callWithAsyncErrorHandling (chunk-YYVLN2RI.js?v=ecbf9ced:1685:17)
    at HTMLInputElement.invoker (chunk-YYVLN2RI.js?v=ecbf9ced:10331:5)

Vue throws a warning with this info:

[Vue warn]: Unhandled error during execution of native event handler 
  at <InputText key=0 ref=fn<bound inputRef> id=null  ... > 
  at <DatePicker unstyled="" showIcon="" iconDisplay="button"  ... > 
  at <App>

Reproducer

https://stackblitz.com/edit/primevue-4-vite-issue-template-1kvrox?file=src%2FApp.vue

PrimeVue version

4.0.0-rc.3

Vue version

3.x

Language

TypeScript

Build / Runtime

Vite

Browser(s)

Chrome 126, Safari 17

Steps to reproduce the behavior

1. DatePicker component with unstyled property
2. Empty input field
3. Open Calendar with the button
4. Click arrow down

Expected behavior

Navigating the calendar should work with arrow keys.

[cjalex1313]

I created this #6155 as a fix

[mikahozz]

This seems to work now, thanks 👍