Accepted files starts out grey then goes to red in dialog

[megbouv]

Bug Report

Describe the bug

On drag and drop initially the dropzone area is grey but then turns to red, but the files are accepted.

Steps to reproduce

Steps to reproduce the behavior:

1. Create dropzone area in a dialog within React Hook Form Controller.
2. set acceptedFiles to 'application/x-pem-file',
   'application/x-x509-ca-cert',
   'application/x-x509-user-cert'
3. Attempt to drag and drop a .pem file. Initially it is showing as accepted (grey) but then turns to rejected (red) but it still allows you to submit.

Expected behavior

A .pem file should be accepted and should not turn red.

### Screenshots

Versions

• mac OS 10.15.6
• Chrome
• @material-ui/core version: 4.11.0
• material-ui-dropzone version: 3.5.0

Additional context

This only happens within a material ui dialog in chrome. The issue does not exists in Firefox or outside of the dialog.