Error with cm_rpt_state

Hello,

in the log I have the following error:

"Error while retrieving properties
for IMetaName <rpt:state>; com.sapportals.wcm.WcmException:
java.lang.NullPointerException: while trying to invoke the method
com.sapportals.wcm.repository.IProperty.getValueAsString() of a null object
loaded from local variable 'property'
"

I found the corresponding Property Metadata:

So the questions are:

1. what's wrong with this property ?

2. what's the use of this property (I find nothing in doc/note/scn) ?

3. how to sove this ?

Thank you.

Vincent