Optimizer Bug of Debug Version

In 8.1, if we execute the following queries on an debug version:

create table t(a int,b int);
create index ttt on t(a,b);
explain select * from t t1,t t2 where (t1.a=1 and t2.b in (1,2)) or (t1.a=2
and t2.b in (3,4));

The server will halt in function "generate_bitmap_or_paths".Seems that
"create_or_index_quals" produces OR-of-OR quals, which is not allowed in
this phase.