added an error message when an element is not found within a <choice> (bug

* relaxng.c: added an error message when an element is not
  found within a <choice> (bug 126093)
diff --git a/relaxng.c b/relaxng.c
index cbc9073..9292497 100644
--- a/relaxng.c
+++ b/relaxng.c
@@ -10029,6 +10029,7 @@
                     }
                     if (list == NULL) {
                         ret = -1;
+			VALID_ERR2(XML_RELAXNG_ERR_ELEMWRONG, node->name);
                         break;
                     }
                     ret = xmlRelaxNGValidateDefinition(ctxt, list);