Export feature does not set UTF-8 as default

[obreil54]

Describe the bug
When I am in the export view and I can select the decode format it says that if you leave it blank it will use UTF-8 by default, however if I do leave it blank it does not use UTF-8.

Reproduction steps
I know this because when I leave it blank it does not decode Russian characters properly, however if I select UTF-8 manually then it then decodes everything as needed.

[cars10]

We have the same issue. The code does not reflect what is stated in the help message:

• the form does not set a default value
• the controller simply passes the blank encoding to the csv_converter
• the csv_converter does not fallback to abstract_model.encoding (like the help message), it only relies on the controller params. so no encoding is set