[N1QL] preparing duplicate name with a different explain statement hangs

1. create an empty bucket default.
2. create primary index on it.
3. prepare a statement through UI:
prepare p1 as explain SELECT * FROM default WHERE k10 > 10 AND k20 > 20 ORDER BY k20;
4. try preparing p1 again as:
prepare p1 as explain SELECT * FROM default WHERE k10 > 10 AND k20 > 20 ORDER BY k20;
We just see a hang.
5. cancel the above query and try select * from system:prepareds, this query also hangs.

Attaching logs.