[BUGFIX] Require mail subject in finisher overrides

Resolves: #83021
Releases: master, 8.7
Change-Id: Ic88731ce7f2b698d39aca6944cf0257a8a758420
Reviewed-on: https://review.typo3.org/54943


Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>

typo3/sysext/form/Configuration/Yaml/FormEngineSetup.yaml

@@ -83,6 +83,7 @@ TYPO3:
               label: 'tt_content.finishersDefinition.EmailToSender.subject.label'
               config:
                 type: 'input'
+                eval: 'required'
             recipientAddress:
               label: 'tt_content.finishersDefinition.EmailToSender.recipientAddress.label'
               config: