[BUGFIX] Fix SQL error in createEntryData

The database field definition for ref_string is limited to varchar(200)
and can cause an SQL error when bigger strings are inserted.
In addition it makes sense to add a mb_substr() to avoid an error if
longer strings are inserted.

Fixes: #79425
Releases: master
Change-Id: I1f1e672f610f830ad5e02509cb1f0529c9cbeb41
Reviewed-on: https://review.typo3.org/51397


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>