MG01: Datetime field empty after update occurrence in DSP.

Summary:
MG01: Datetime field empty after update occurrence in DSP.

Symptoms:
An update is done on an occurrence without changing the value of the datetime
field.
The datetime field is now empty after this update in the DSP.
This problem occurs since service pack MG02.

An example:
Datetime values are maintained via the write trigger:
if ($dbocc("MYENTITY") = 0)
INSERTDATETIMEFIELD.MYENTITY = $datim
endif
write

On insert the datetime field INSERTDATETIMEFIELD.MYENTITY fills correct.
After an update the datetime field INSERTDATETIMEFIELD.MYENTITY is empty.