Cannot index by a variety of types in the same level error.

Hello

I'm facing the following issue. 

I have a gridLayout which is selectable and the data is from a local!getquery, 

• The issue i'm facing happens when the user clicks the top selection to unselect ALL.
• If the user unselect 1 by 1 works fine.

The reason why i'm doing is to get the selected rows and send them to a Post and a Put method i have so you don't necessarily need to send the entire set.

I know i can do a workaround for the process model to work but i'm trying to understand technically why the option *Unselect-all is breaking the following code.

selectionSaveInto: {
      a!save(ri!selectedValues,      
        save!value ),
      if(rule!APN_isBlank(ri!selectedValues)  ,
      a!save(ri!errorsToSend,null),
      a!save(ri!errorsToSend,index(local!errorSubset,ri!selectedValues))
      )

        
 
    }
  )

Somehow after unselecting all at the sametime is falling under the false statement. IF i do 1 by 1 works fine.

Already did some tests and the expression is falling into true outside that saveinto{}.

I was verifying that the code for 19.1 for that section is not working properly. Is this an Appian bug or it's something i'm not doing right? 

https://docs.appian.com/suite/help/19.1/Editable_Grid_Component.html  * Editable Grid with Selection