summary

<amp-ad> accepts an optional json attribute. Some websites provide a string in that attribute which is technically valid json (as would be a number). This becomes a problem when attempting to assign to a property of jsonTargeting. It fails silently in sloppy mode, but will throw in both esm and strict mode.

@keithwrightbos: Do you know what the behavior should be in the case of a string json value? (or any non truthy non-object for that matter).