fix use of asyncDrawable

src/main/java/com/owncloud/android/ui/fragment/FileDetailFragment.java

@@ -589,7 +589,7 @@ public class FileDetailFragment extends FileFragment implements OnClickListener
                                 );
                         iv.setVisibility(View.GONE);
                         v.setVisibility(View.GONE);
-                        previewImage.setImageBitmap(resizedImage);
+                        previewImage.setImageDrawable(asyncDrawable);
                         activatePreviewImage();
                         previewLoaded = true;
                         task.execute(getFile());