WP CLI get action command: correct parentheses/nesting of conditional checks.

[barryhughes]

When looking at #1271, I noticed a problem with the wp action-scheduler action get <id> command. This command was mostly functional, but also generated a warning relating to its handling of the --fields flag:

PHP Warning:  Undefined array key "fields" in /.../wp-content/plugins/action-scheduler/classes/WP_CLI/Action/Get_Command.php on line 27

The problem was a small oversight in the line used to check if this flag was set.

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Steps to replicate

1. First, identify an existing scheduled action and note down the ID.
   1. An easy way to do this is to run wp action-scheduler action list and grab the first ID.
   2. In the event you don't have any actions, you can generate one with wp eval "as_enqueue_async_action( 'test' );" (or else you can use wp action-scheduler action create test now once Import get_flag_value() from WP_CLI\Utils before using. #1271 has been merged).
2. Using the current stable release (3.9.2), try running wp action-scheduler action get <ID> and you should see the same error noted in the PR description.
3. Switch to this branch and repeat, the error should be solved.
4. Confirm that the --fields flag still works as expected by running wp action-scheduler action get <ID> --fields=hook,status.

Changelog

Fixes a problem with wp action-scheduler action get and its handling of the --fields flag.

[barryhughes]

✍🏼 Note that the same challenge with PhpUnit noted here is impacting the test results.

[crstauf]

@barryhughes Are the parentheses around the second conditional necessary at this point?

[barryhughes]

Not strictly necessary, if I'm reading correctly, because we'd get exactly the same result without them (&& having higher precedence than ||). That said, this makes things clearer (imo) if one doesn't recall the rules of operator precedence.

[prettyboymp]

Changes look good.