fix js error

apps/files_sharing/js/public.js

@@ -16,7 +16,7 @@ $(document).ready(function() {
 	if (typeof FileActions !== 'undefined') {
 		var mimetype = $('#mimetype').val();
 		// Show file preview if previewer is available, images are already handled by the template
-		if (mimetype.substr(0, mimetype.indexOf('/')) != 'image' && $('.publicpreview').length() !== 0) {
+		if (mimetype.substr(0, mimetype.indexOf('/')) != 'image' && $('.publicpreview').length === 0) {
 			// Trigger default action if not download TODO
 			var action = FileActions.getDefault(mimetype, 'file', OC.PERMISSION_READ);
 			if (typeof action === 'undefined') {