Fix #14367: Dropdown selected item template

[ty-ler]

Fixes #14367

I didn't want to create a duplicate issue for this problem, but did create a very simple demo of the issue in Stackblitz:
https://stackblitz.com/edit/stackblitz-starters-xxhaw6?file=src/main.ts

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Name	Status	Preview	Comments	Updated (UTC)
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[rosenthalj]

Issue #14367 is really two bugs :

1. Having {{ item.label }}
   throws Cannot read properties of undefined (reading 'label') error if no item is selected initially
2. if you have [filter]="true" and you have a selected an item, then start typing in the filter input the selected item is not displayed
   (Note: these descriptions were taken directly from this "Describe the bug" section at the top of issue Component: Dropdown #14367)

After examining the changes in this pull request #14643, it appears that only the first bug of issue #14367 is fixed by this pull request. The "very simple demo" reproducer provided in this pull request only attempts to fix the first bug.

Pull request #14665 fixes the second bug of issue #14367

[ty-ler]

Yes, this PR is basically just to address the first bug regarding the selected item template.