Detail of all email attachments that are associated to a case.

I want to show in Cases section, in a detail, all email attachments that are associated the case.

For this I have done the following steps:

1-Created a database view that get all email attachments that are associated to a cases.

2-Create the object in the /0/dev console. 

3-Create a detail with the detail wizard.

4-Chage base object of the detail as said in:

https://academy.bpmonline.com/documents/technic-sdk/7-13/adding-attachm…

After all this done, the detail is being shown but it doesn't show any record, and it throws some errors in the browser console:

Are the steps I have done correct?

What could be causing this error? 

Regards, 

Javier