• bug fix
• BC break? no

We are using Tracy support for scrubbing to remove passwords etc. from our Tracy bluescreen files. But we've found that in following part of stacktrace (in Elasticsearch\Transport from official Elasticsearch SDK), password remained:

connectionParams: array
    'client' => array
        'x-elastic-client-meta' => true
        'curl' => array
            107 => 1
            10005 => 'actualHostHere:actualPasswordHere'

It's because Describer doesn't apply scrubber on non-string keys. This PR argues that they have to be for sanity checked as well. I've chosen the path of not changing Scrubber signature, so I cast scalar keys to strings and pass empty string for non scalar keys. To be honest I am not sure whether such eventuality is possible (I was thinking about WeakMap and stuff like that, but not sure if it would make its way there).