Queue operations check always returns true, even for unselected operations

In sf_queue.module, the sf_queue_salesforce_api_pre_export performs a check to see if the current operation (create, update, delete) is in the list of 'cron_operations' using an in_array call.

However, when options are unticked in the salesforce/fieldmap/%id settings page, they are still in the array, but with a value of '0'. For this reason, the in_array call will always return true, even if an operation is unchecked.

Just for illustration's sake, here is an example structure of the variable 'sf_queue_settings':

Array
(
    [cron_operations] => Array
        (
            [update] => update
            [delete] => delete
            [create] => 0
        )

    [cron_frequency] => 0
    [cron_period] => .25
    [cron_num_objects] => 200
    [cron_min_threshold] => 0
    [retry_num_attempts] => 0
)

As you can see in 'cron_operations', the 'create' key still exists, and thus will return true for an in_array() check.