correct the bug #67081 fix

Author: weltling

ext/dom/documenttype.c

@@ -211,7 +211,7 @@ int dom_documenttype_internal_subset_read(dom_object *obj, zval **retval TSRMLS_
 				xmlOutputBufferFlush(buff);
 
 #ifdef LIBXML2_NEW_BUFFER
-				smart_str_appendl(ret_buf, xmlOutputBufferGetContent(buff), xmlOutputBufferGetSize(buff));
+				smart_str_appendl(&ret_buf, xmlOutputBufferGetContent(buff), xmlOutputBufferGetSize(buff));
 #else
 				smart_str_appendl(&ret_buf, buff->buffer->content, buff->buffer->use);
 #endif