Function quote_nullable(timestamp without time zone) is not unique

Question

When I run this query on "enterprisedb 9.2", it raises an error:

select quote_nullable(to_date('09-02-2014 ','dd-MM-yyyy'))::date;

Error:

LINE 1: select quote_nullable(to_date('09-02-2014 ','dd-MM-yyyy'))::...
               ^
HINT:  Could not choose a best candidate function. You might need to add explicit type casts.
********** Error **********

ERROR: function quote_nullable(timestamp without time zone) is not unique
SQL state: 42725
Hint: Could not choose a best candidate function. You might need to add explicit type casts.
Character: 8

In Postgresql 9.1, this query above run ok.

Please tell me what is happening here. Why is the function quote_nullable(timestamp without time zone) not unique?