Fix incorrect condition in CliLogger::message() method

[MahdiBagheri71]

Expected behavior:
The channel_data should be decoded correctly.

Proposed fix:
Replace the condition in the if statement with the correct one:

if (isset($message['data']['channel_data']) && is_string($message['data']['channel_data'])) {
    $message['data']['channel_data'] = json_decode($message['data']['channel_data'], true);
}

[taylorotwell]

I am closing this pull request because it lacks sufficient explanation, tests, or both. It is difficult for us to merge pull requests without these things because the change may introduce breaking changes to the framework.

Feel free to re-submit your change with a thorough explanation of the feature and tests - integration tests are preferred over unit tests. Please include it's benefit to end users; the reasons it does not break any existing features; how it makes building web applications easier, etc.

Thanks!