Handle null uniqueColumns.

src/main/java/com/samskivert/jdbc/HsqldbLiaison.java

@@ -129,11 +129,13 @@ public class HsqldbLiaison extends BaseLiaison
 
         // note the set of single column unique constraints already provided (see method comment)
         Set<String> seenUniques = new HashSet<String>();
+        if (uniqueColumns != null) {
             for (List<String> udef : uniqueColumns) {
                 if (udef.size() == 1) {
                     seenUniques.addAll(udef);
                 }
             }
+        }
         // primary key columns are also considered implicitly unique as of HSQL 2.2.4, and it will
         // freak out if we also try to include them in the UNIQUE clause, so add those too
         seenUniques.addAll(pkColumns);