[BUGFIX] Saving a scheduler task throws fatal error

The backport of commit:357ce730 for version 4.7 was applied to the
"update" code instead of the "save" code. This patch moves the change to
the right place.

Change-Id: I8917a4161b5221eaf3041bad78713813ff18a0d3
Fixes: #48022
Related: #44152
Follow-up to: 05d35ee3cff633c82e440a452b6a08690cdc4092
Releases: 4.7
Reviewed-on: https://review.typo3.org/20638
Reviewed-by: Stephan Großberndt
Tested-by: Stephan Großberndt
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn