I try to create an automation chain to get elements of a folder and put them in my document (inherit metadata).
I have 3 metadata in my folder, and I want to “copy” values in my metada's document. But it doesn't work for multi-valued and date metadata
In automation chain I do :

 - Fetch > Context Document
 - Push & Pop > Push Document
 - Document > Get Parent
 - Execution Context > Set context Variable
   - name = v_field_mutivalued
   - value = expr:@{Document["gen:field_multivalued"]}
 - Execution Context > Set context Variable
   - name = v_field_text
   - value = expr:@{Document["gen:field_text"]}
 - Execution Context > Set context Variable
   - name = v_field_date
   - value = @{Fn.calendar(Document["gen:field_date"])}
 - Push & Pop > Pop Document
 - Document > Update Property
   - value:@{v_field_date.date}<br/>
   - xpath:gen:field_date     
 - Document > Update Properties
   - gen:field_multivalued=@{v_field_multivalued}<br/>
     gen:field_text=@{v_field_text}<br/>

In “gen:field_multivalued” it stored : [Ljava.lang.String;@4c28a60
In “gen:field_text” it's OK
In “gen:field_date” : it's OK BUT when the date is NULL it makes an error (Caused by: [Error: v_field_date.date: null] [Near : {… Unknown ….}] (I don't put all the log because is too big !) What is wrong for multivalued field and how test null value ?
Thanks in advance