Dragging a directory into sample files screen causes an upload attempt and internal error

[JeffreyThiessen]

Describe the bug

The click or drag window accepts directories, when it shouldn't.

Steps to reproduce the problem

What were you doing when you encountered the problem?

1. Create a sample on a project
2. go to the files tab
3. drag a directory into the "click or drag" area

Expected behaviour

Only sequence files should be able to be dragged into the upload area
Nothing should happen when dragging in a directory, just like if you try to drag in a .txt file

When you click the bar instead, you cannot select a directory to upload, it just opens the directory so you can select a file, as expected.

Additional context

I have only tested this on Linux Gnome, not sure if it exists with Windows Explorer too.