SQLite OperationalError when empty or_() used in query with multiple filters.

When an empty or_() is passed to a query with multiple .filter() calls, it adds an empty () to the SQL. SQLite errors on this. I've tested this in the current release of 0.7.2, and the error also occurs in the latest (as of writing) snapshot of 0.7.3.

The error thrown:

sqlalchemy.exc.OperationalError: (OperationalError) near ")":
syntax error u'SELECT test.id AS test_id \nFROM test \nWHERE test.id = ? AND ()' (1,)

For a real world example, I'm appending to an or_() in a loop, the loop may not add any conditions, my code looks something like this:

    for user in user_ids:
        disjunction.append(User.id == user)

    query = query.filter(disjunction)

The bug isn't too serious, my current workaround is simple and does the job, but it would be useful for this to be fixed regardless:

    if len(user_ids) > 0:
        for user_id in user_ids:
            disjunction.append(User.id == user_id)

        query = query.filter(disjunction)

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