TYPO3 Core

The Administration Log gets entries like:

Core: Error handler (FE): PHP Warning: Invalid argument supplied for foreach() in .../typo3/sysext/form/Classes/Domain/Finishers/EmailFinisher.php line 337

Problem in Line 337 of EmailFinisher.php:
L337: foreach ($recipients as $address => $name) {

If $recipients is not an array the warning occurs!
So we must get sure, that $recipients is cast to an array like the following code:

Solution-Proposal: (tested and worked) replace L337 with the following code

L337: foreach ( (array) $recipients as $address => $name) {

Good Luck