If an error is thrown during fastboot rendering it still returns a 200 instead of non-200

**Issue**: Fastboot responds with a `200` when an error is thrown during the fastboot rendering cycle, however it is unpredictable to say that the rendering was successful. In most cases, there will be some level of mangled HTML returned by fastboot. This also makes writing tests against fastboot error scenarios difficult because there is no way to know there was an error encountered other than by checking that rendered state is missing from the delivered HTML payload.

**Expectation**: Fastboot should return a non-`200` and allow for the application error handling to enter an error substate.

**Reproduction Repo**:
https://github.com/rileyhilliard/fastboot-errors