[BUG] Parse_json failed when attributes undefined

[sashalarsoo]

Hi got this error :

Caused by: java.lang.IllegalArgumentException: '=~' requires left operand to be String.

for this config even i checked attributes in null :

- parse_json:
            source: "/body"
            destination: "/attributes/resource.attributes.envoy"
            parse_when: '/attributes/resource.attributes.k8s.pod.name != null and /attributes/resource.attributes.k8s.pod.name =~ ".*envoy-gateway.*"'