[BUGFIX] DBAL's quoteFieldNames() returns an empty string

DBAL's DatabaseConnection::INSERTquery() builds an array. The keys
(fields) are mapped through quoteFieldNames(), which returns an empty
string. DBAL's SqlParser tries to use $GLOBALS['TYPO3_DB'], which is
not available here.

Resolves: #56306
Releases: 6.2
Change-Id: I97eff8f796fcb8d530d16ff5f6111ebd5d28d5ce
Reviewed-on: https://review.typo3.org/27864
Reviewed-by: Markus Klein
Tested-by: Markus Klein