Exporting multiple file formats concatenates the types, resulting in the wrong type being downloaded.

[AdamGAmar]

Describe the bug
When exporting multiple file formats, parameters from the previous exports are preserved. It becomes unclear which format the user wished to download, and often the wrong one is returned.

Reproduction steps
In the demo app, export to JSON, then XML. Observe that JSON will download twice.

Expected behavior
The chosen format should download.

Additional context

• rails_admin version: 3.3.0
• rails_admin npm package version: 3.3.0