BUG #13168: DROP DATABASE does not clean up all references

The following bug has been logged on the website:

Bug reference: 13168
Logged by: Cees van Zeeland
Email address: cees(dot)van(dot)zeeland(at)xs4all(dot)nl
PostgreSQL version: 9.4.1
Operating system: Windows 7 Home Edition 64 bit
Description:

-- Follow the next steps to produce an unexpected error
-- The next 16 lines work fine
CREATE DATABASE new
WITH ENCODING='LATIN1'
TEMPLATE=template0
LC_COLLATE='C'
LC_CTYPE='C'
CONNECTION LIMIT=-1;

DROP TABLE IF EXISTS category CASCADE;
CREATE TABLE category
(
category_id SERIAL PRIMARY KEY
,category_name varchar(30) NOT NULL
,category_description varchar(200) NOT NULL
);

-- Now I am going to repeat the same script without DROP TABLE
-- After the next line, I assume that all old references within the database
are gone
DROP DATABASE new;

CREATE DATABASE new
WITH ENCODING='LATIN1'
TEMPLATE=template0
LC_COLLATE='C'
LC_CTYPE='C'
CONNECTION LIMIT=-1;

-- Here I leave out the line with DROP TABLE
-- It results to the error message:
-- ERROR: relation "category" already exists
-- Is this a bug or am I missing something?
-- DROP TABLE IF EXISTS category CASCADE;

CREATE TABLE category
(
category_id SERIAL PRIMARY KEY
,category_name varchar(30) NOT NULL
,category_description varchar(200) NOT NULL
);

DROP DATABASE new;

-- In fact I can repeat this script
-- first time: no error
-- second time: with error