adjust callback error reporting
adjust callback error reporting

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