If a variable value is set to null or a variable is removed, then the entry in ACT_HI_VARINST should be removed. An entry to ACT_HI_DETAIL should be added nevertheless. This behavior must be configurable and disabled by default in order to not break existing behavior.

Motivation:

• For some users, null value variables have no relevance. This feature reduces the volume of entries in ACT_HI_VARINST for them.

Implementation hints:

• This could be an engine configuration property or it could be a separate HistoryEventHandler implementation that users can configure