[BUGFIX] Fix several undefined array key issues in DataHandler scope

DataMapProcessor tries to access `$possibleChainedIds[0]` which
might not be defined, since that array is the result of a previous
`array_intersect` invokation, which keeps the array keys of the
original input array.

DataHandler tries to access `$this->copyMappingArray[$table][$uid]`,
which might not be defined in case the previous copy command could
not be executed (e.g. since the record was deleted already).

Resolves: #101748
Releases: main, 12.4, 11.5
Change-Id: Ibcbc412c7df62ce17dfa2c0f6fc120ccebb953d8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80670


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>