Load previews only for registered providers

controller/documentcontroller.php

@@ -169,6 +169,7 @@ class DocumentController extends Controller{
 				$documents[$key] = $document;
 			}
 			$documents[$key]['icon'] = preg_replace('/\.png$/', '.svg', \OCP\Template::mimetype_icon($document['mimetype']));
+			$documents[$key]['hasPreview'] = \OC::$server->getPreviewManager()->isMimeSupported($document['mimetype']);
 			$fileIds[] = $document['fileid'];
 		}
 

js/documents.js

@@ -61,7 +61,7 @@ $.widget('oc.documentGrid', {
 		previewURL = OC.generateUrl('/core/preview.png?') + $.param(urlSpec);
 		previewURL = previewURL.replace('(', '%28').replace(')', '%29');
 		
-		if ( $('#previews_enabled').length ) {
+		if ( $('#previews_enabled').length && document.hasPreview) {
 			var img = new Image();
 			img.onload = function(){
 				var ready = function (node){