Select Query Not Fetching Records In 11g?

I have a Select query which is not fetching records in 11g (11.2.0.2.0) but working fine in 10g (10.2.0.4.0). The query is as below.

--CREATE TABLE t1 (col1 NUMBER, col2 VARCHAR2 (15 CHAR), flag varchar2(1))

--insert into t1(col1, col2, flag) values(1, 'a', 'Y');
--insert into t1(col1, col2, flag) values(2, 'b', 'N');

SELECT *
FROM t1 x
WHERE col1 = 1 AND col2 = 'a' -------------- condition1
AND 0 = -------------- condition2
NVL (
(SELECT COUNT (1)
FROM t1 y
WHERE y.flag = 'N'
AND x.col1 = y.col1
AND x.col2 = y.col2),0)--=0

When remove NVL function or change the condition by having AND NVL(SELECT) =0 the query working fine.