[TASK] Check whether data was successfully imported in the functional test

Exception is thrown when fixture data can not be loaded into database.

Resolves: #51783
Releases: 6.2
Change-Id: If23657555940cb98954e0ec72ee7d8be53bea1b4
Reviewed-on: https://review.typo3.org/23640
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe