Type casting error on MySQL time field for TCA type input / dbType time saving empty time field
I'm trying to have a time input in TYPO3 9 LTS working together with MySQL 5.7.24.
In the ext_tables.sql the field gets defined like this:
some_field time default NULL
In the TCA the field gets defined like this:
'some_field' => [ 'exclude' => 1, 'label' => 'Some field', 'config' => [ 'type' => 'input', 'dbType' => 'time', 'eval' => 'time', ], ],
When saving the record in the backend without a time input (which should be possible) I'm getting the error:
These fields of record 1 in table "some_table" have not been saved correctly: some_field! The values might have changed due to type casting of the database.
When looking at the database record the "some_field" field gets the value "00:00:00" (although the db default is NULL). So I would think that TYPO3 does save here some unexpected default value which gets casted by the database to "00:00:00".
When selecting a time the record can be saved and opened without error. So this does work fine. So there is just a problem with when saving the empty field