Fix: Content picker check whether item.subtype is truthy before using it

[fabiankaegy]

Description of the Change

The ContentPicker can be used to fetch items of different types. Taxonomy Terms for example. These don't have a subtype property defined. But unlike the code assumed the actual subtype key is sometimes present but the value is undefined. This case is now also handled.

Closes #335

How to test the Change

Changelog Entry

Fixed - Don't delete picked items if the subtype is not set

[github-actions]

Size Change: +11 B (+0.02%)

Total Size: 63.5 kB

Filename	Size	Change
dist/index.js	63.5 kB	+11 B (+0.02%)

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