Fix unability to RelaxNG-validate grammar with choice-based name class

Previously, test/relaxng/ambig_name-class2.xml would fail to validate
against test/relaxng/ambig_name-class2.rng:

> test/relaxng/ambig_name-class2.rng:4:
>   element attribute: Relax-NG parser error :
>       Found anyName attribute without oneOrMore ancestor
> Relax-NG schema test/relaxng/ambig_name-class2.rng failed to compile
Signed-off-by: Jan Pokorný <jpokorny@redhat.com>

relaxng.c

@@ -6395,7 +6395,10 @@ xmlRelaxNGCheckRules(xmlRelaxNGParserCtxtPtr ctxt,
                            NULL, NULL);
             }
             if ((!(flags & XML_RELAXNG_IN_ONEORMORE))
-                && (cur->name == NULL)) {
+                && cur->name == NULL
+                /* following is checking alternative name class readiness
+                   in case it went the "choice" route */
+                && cur->nameClass == NULL) {
                 if (cur->ns == NULL) {
                     xmlRngPErr(ctxt, cur->node, XML_RNGP_ANYNAME_ATTR_ANCESTOR,
                                "Found anyName attribute without oneOrMore ancestor\n",

result/relaxng/ambig_name-class2_err

+./test/relaxng/ambig_name-class2.rng validates

test/relaxng/ambig_name-class2.rng

+ambig_name-class.xml
\ No newline at end of file

test/relaxng/ambig_name-class2.xml

+<foo alpha="all"/>