TYPO3 Core

#102495 ensured that the `ext_tables.sql` scanning using
the own sql parser set column comments to an empty string
instead of using the default of null.

This has been done as a preparation for the next Doctrine
DBAL major version upgrade.

Due to the fact that the doctrine `Column` does not contain
the "string" enforcement this now means that empty comments
are detected as changes for PostgreSQL.

It does not make sense to extend and replace all the classes
of doctrine to reflect the upcoming changes, therefore this
change is reverted.

The original intention needs to be included with the major
Doctrine DBAL upgrade.