#3840 PG: functions loading fix (PG <= 8.3)

plugins/org.jkiss.dbeaver.ext.postgresql/src/org/jkiss/dbeaver/ext/postgresql/model/PostgreSchema.java

@@ -786,7 +786,8 @@ public class PostgreSchema implements DBSSchema, DBPNamedObject2, DBPSaveableObj
         @Override
         public JDBCStatement prepareLookupStatement(@NotNull JDBCSession session, @NotNull PostgreSchema owner, @Nullable PostgreProcedure object, @Nullable String objectName) throws SQLException {
             JDBCPreparedStatement dbStat = session.prepareStatement(
-                "SELECT p.oid,p.*,pg_catalog.pg_get_expr(p.proargdefaults, 0) as arg_defaults,d.description\n" +
+                "SELECT p.oid,p.*," +
+                    (session.getDataSource().isServerVersionAtLeast(8, 4) ? "pg_catalog.pg_get_expr(p.proargdefaults, 0)" : "NULL") + " as arg_defaults,d.description\n" +
                     "FROM pg_catalog.pg_proc p\n" +
                     "LEFT OUTER JOIN pg_catalog.pg_description d ON d.objoid=p.oid\n" +
                     "WHERE p.pronamespace=?" +