Error on updating deleted Mailing

[Nikdro]

Steps to reproduce:

• Create a new Mailing in Neos
• Send Mailing to CleverReach
• Delete Mailing in CleverReach
• Try to Update Mailing in Neos -> ERROR

Idea:
Catch this explicit error and create a new Mailing at CleverReach, if ID of the existent is not existing anymore.