added database variable declaration when checking extensions when using a custom user-agent

[definity]

If a customer user-agent is defined using the command-line argument --agent the script fails with the following error

 [+] Extension Search
Traceback (most recent call last):
  File "./typo3scan.py", line 199, in <module>
    main.run()
  File "./typo3scan.py", line 86, in run
    conn = sqlite3.connect(database)
                    check_404 = check.check_404()
UnboundLocalError: local variable 'database' referenced before assignment

The database variable is only ever set on line 43. This is part of the if/else statement that checks if the --agent command-line arg was present. See below.

        if (args.user_agent):
            user_agent = args.user_agent
        else:
            database = os.path.join(self.__path, 'lib', 'typo3scan.db')
            conn = sqlite3.connect(database)
            c = conn.cursor()
            c.execute('SELECT * FROM UserAgents ORDER BY RANDOM() LIMIT 1;')
            user_agent = c.fetchone()[0]
            c.close()

[definity]

Not sure if this is how you want to fix this bug, but it works. Ideally it might be better to define it once outside any conditional statements to avoid the duplication.