[BUGFIX] Prevent sql errors with missing ColumnMap

If the TCA configuration for an object is missing
no ColumnMap can be generated which leads to sql
errors in method addUnionStatement in Typo3DbBackend.
Instead an Exception should be thrown.

Releases: 6.0, 6.1
Fixes: #7267
Change-Id: Ie364d2199be3d1e0128811e0cc41ff7ad210324b
Reviewed-on: https://review.typo3.org/16536
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Reviewed-by: Alexander Schnitzler
Tested-by: Alexander Schnitzler