Customizer Uploader doesn't handle large files properly

[pento]

Both of these tests were with image files larger than the max file size - 3MB images with a 2MB max file size:

Dragging the file onto the upload area, the browser window redirects to the location of the local file, the same as if the file were dragged to a non-dropzone area.

When using the file browser to select the file, the upload fails silently.

In both cases, an error similar the Media Uploader would be preferable.

I was able to reproduce this bug and also noticed that if you try to "select a file" it does nothing, no error etc if the file is too large.