[BUGFIX] Fix Undefined array key warning in InlineRecordContainer

Fix undefined array key 0 in `InlineRecordContainer` by adding
a null coalescing operator and handling `$uid` properly.

Resolves: #101682
Releases: 11.5
Change-Id: I510c4af4dacfd9b1fb8110bf43b192c87918450f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80548


Reviewed-by: J�rg B�sche <typo3@joergboesche.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan B�rk <stefan@buerk.tech>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan B�rk <stefan@buerk.tech>