Fix core dump in transformValuesClause when there are no columns.

The parser code that transformed VALUES from row-oriented to
column-oriented lists failed if there were zero columns.
You can't write that straightforwardly (though probably you
should be able to), but the case can be reached by expanding
a "tab.*" reference to a zero-column table.

Per bug #17477 from Wang Ke.  Back-patch to all supported branches.

Discussion: https://postgr.es/m/17477-0af3c6ac6b0a6ae0@postgresql.org

src/test/regress/sql/select.sql

@@ -148,6 +148,11 @@ SELECT 2+2, 57
 UNION ALL
 TABLE int8_tbl;
 
+-- corner case: VALUES with no columns
+CREATE TEMP TABLE nocols();
+INSERT INTO nocols DEFAULT VALUES;
+SELECT * FROM nocols n, LATERAL (VALUES(n.*)) v;
+
 --
 -- Test ORDER BY options
 --