Use webtorrent-hybrid for server webtorrents

app/lib/components/FileSharing/FileEntry.jsx

@@ -148,7 +148,7 @@ class FileEntry extends Component
 export const FileEntryProps = {
 	data : PropTypes.shape({
 		name    : PropTypes.string.isRequired,
-		picture : PropTypes.string.isRequired,
+		picture : PropTypes.string,
 		file    : PropTypes.shape({
 			magnet : PropTypes.string.isRequired
 		}).isRequired,