ContenElementWrappingService needs safeguard for date unserialization
The service only checks if a date-typed node property is != NULL, but doesn't check if it is actually a DateTime object. In some cases, the property might be an empty string or ... whatever. These edge cases should at least not end with a fatal error.
[TASK] Additional check for date properties
This adds another check to make sure that corrupt or unexpected values
of date node properties don't lead to a fatal error caused by calling
methods on a non-object.