erroneously ignores a validation error if no error callback set

Reported by Stefan Behnel
https://bugzilla.gnome.org/show_bug.cgi?id=724903
diff --git a/valid.c b/valid.c
index aedd9d7..1e03a7c 100644
--- a/valid.c
+++ b/valid.c
@@ -2633,11 +2633,8 @@
 	/*
 	 * The id is already defined in this DTD.
 	 */
-	if ((ctxt != NULL) && (ctxt->error != NULL)) {
-	    xmlErrValidNode(ctxt, attr->parent, XML_DTD_ID_REDEFINED,
-	                    "ID %s already defined\n",
-			    value, NULL, NULL);
-	}
+	xmlErrValidNode(ctxt, attr->parent, XML_DTD_ID_REDEFINED,
+			"ID %s already defined\n", value, NULL, NULL);
 #endif /* LIBXML_VALID_ENABLED */
 	xmlFreeID(ret);
 	return(NULL);