fix warning.
fix warning.

tcjuan/pdfjs_viewer-rails,NetsoftHoldings/pdfjs_viewer-rails,senny/pdfjs_viewer-rails,tcjuan/pdfjs_viewer-rails,gordonbisnor/pdfjs_viewer-rails,gordonbisnor/pdfjs_viewer-rails,gordonbisnor/pdfjs_viewer-rails,senny/pdfjs_viewer-rails,NetsoftHoldings/pdfjs_viewer-rails,tcjuan/pdfjs_viewer-rails,NetsoftHoldings/pdfjs_viewer-rails,senny/pdfjs_viewer-rails