delete-button: call error callback on delete error
delete-button: call error callback on delete error

SimonWaldherr/uploader,SimonWaldherr/uploader,FineUploader/fine-uploader,SimonWaldherr/uploader,FineUploader/fine-uploader,SimonWaldherr/uploader,SimonWaldherr/uploader,FineUploader/fine-uploader,SimonWaldherr/uploader,SimonWaldherr/uploader