Rainbow throws an error when a site uses `postMessage()`

[Danziger]

Depending on the format, Rainbox might throw the following error, instead of simply ignoring the message:

[DanielSinclair]

Working on a fix for this soon! It should only appear as an issue in local dev environments currently

[0xbuidler]

@DanielSinclair Is this fixed in local dev as well ?