handle crashing_thread = None case

[willkg]

In this code:

https://github.com/mozilla/fx-crash-sig/blob/5f779ef19efb85f9148bf759e92903db313be72c/fx_crash_sig/symbolicate.py#L50-L52

it doesn't handle the case where crashing_thread=None. It should probably do the same thing it does when the crashing_thread >= len(threads).

[willkg]

I have a crash_ping_sample.json file where the crashing_thread value is a "0".

However, the schema specifies it can only be an integer and has to have a minimum of 0. It can't be a null and can't be a string.

https://github.com/mozilla-services/mozilla-pipeline-schemas/blob/f6e9491adec9d8c225b219222cd657fe7d982997/schemas/telemetry/crash/crash.4.schema.json#L1625-L1627

So... maybe the sample data I've got is bad and I should get some new sample data.

[willkg]

I looked at the data and crashing_thread is in stack_traces.crash_info both of which are nullable, but crashing_thread itself can't be a null. There's some code checking all those things, so I think we're fine there.

Regardless, crashing_thread can't be a string, so the issue here is that something is wrong with the crash ping sample. Closing this out.