Passing Nulls from web elements to a crystal report

I would like to set a parameter value to be sent from the web element WESelect to be null. The crytal report is BEX Query based.

I have tried:

1) sending a blank

2) [#]

3) [0VERSION].[#]

The result always is that the crytsal report parameter screen pops up. Even though it does set the pamaer to null:

New value: ...

Add

Current value: null

Set to null.

I want the parameter screen not to pop up. If I send any other value than null, all works well.

Any suggestions? Thanks