Index: modules/og_user_roles/og_user_roles.module
===================================================================
--- modules/og_user_roles/og_user_roles.module	(revision 1603)
+++ modules/og_user_roles/og_user_roles.module	(working copy)
@@ -2630,9 +2630,11 @@
 //        $file = db_fetch_object(db_query("SELECT u.nid FROM {files} f INNER JOIN {upload} u ON f.fid = u.fid where f.filepath like '%s'", '%' . $basename));
         $file = db_fetch_object(db_query("SELECT u.nid FROM {files} f INNER JOIN {upload} u ON f.fid = u.fid where f.filepath like '%s'", '%' . '/' . $basename));
 		$nid = $file->nid;
-        $gid = og_user_roles_getgid($nid, $uid);
-        $group_node = node_load($gid);
-        og_set_group_context($group_node);
+        if ($nid) {
+          $gid = og_user_roles_getgid($nid, $uid);
+          $group_node = node_load($gid);
+          og_set_group_context($group_node);
+        }
 	  }
 	}