File Extension validation error displayed, even if user decide not to upload file after trying an invalid extension

Hi

We use IMCE-FileField for uploading images,video,pdfs. We are facing a problem while uploading files with invalid extensions.

Steps to replicate:
1. Open IMCE File browser, upload any document with an unsupported extension. For eg. .pdf for a video field.
2. An error message is thrown and file is not uploaded.
3. Try uploading another file, with supported extension For eg. .flv in this instance. The file is uploaded and form submit works.
4. If user does not upload another file(omit step 3), and try to save the node, the invalid extension error is still thrown from file field.

I tried to clear the field, after the #upload_validators call. But could not find a way to do it. Any help in clearing the error, if user decide not to upload the file, after trying an invalid extension is appreciated.

Thanks!