500 when error stack trace is empty

Summary

(Summarize the bug encountered concisely)

Steps to reproduce

Create a Sentry error with no stack trace (you can do this by just raising an error in a rails console)

What is the current bug behavior?

Screen_Shot_2019-12-20_at_11.11.06_AM

What is the expected correct behavior?

We shouldn't 500. Perhaps the frontend should show something like 'No stacktrace'?