Fix wrong placeholder in the validation error message.

Problem/Motivation

In the validation error message, instead of the file name, the '@label' placeholder was showing up. There's a bug in the code, instead of '@label' it should be '@name'

Steps to reproduce

Install the module and upload a file that will cause a validation error, for example, an entry with the same URL destination as source. In the error message instead of file name, the '@label' placeholder will show up.

Proposed resolution

Replace '@label' with '@name' placeholder.

Remaining tasks

User interface changes

API changes

Data model changes