Fix error in clearStoredFiles when listElement is null.
Fix error in clearStoredFiles when listElement is null.

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