null check stacks in isSameStacktrace

[uforic]

Description

Some libraries, such as Mapbox, throw errors that are malformed. They don't have the frames variable, which get used in "_isRepeatData".

This causes Raven.captureException to fail on the second call, on _isRepeatData when deduping errors. This is particularly nasty because it's occurring in the catch part of a try / catch.

Sample code:

    try {
      const attemptedMap = new mapboxgl.Map({
        container: this.mapRef.current,
        style: this.getMapStyle(),
        center: initialCenter,
        zoom: initialZoom,
      });
 } catch (e) {
      // error thrown here
      Raven.captureException(e, {
        level: "warning",
        stacktrace: true});
}

Exception seen in FullStory:

TypeError: Cannot read property 'length' of undefined at d (vendor.bd501d31eb3dbf1fd2b5.js:23:30798) at s._isRepeatData (vendor.bd501d31eb3dbf1fd2b5.js:23:25059) at s._sendProcessedPayload (vendor.bd501d31eb3dbf1fd2b5.js:23:26662) at s._send (vendor.bd501d31eb3dbf1fd2b5.js:23:26417) at s._processException 

I'm not sure what the preferred behavior is here (returning true or false), but it strikes me that returning false is safer.

Appreciate any feedback, thanks!

[kamilogorek]

Looks good. Could you also add a quick test covering this scenario? (I also just realized that we don't have tests for this util at all...)

[uforic]

The lint script runs prettier automatically, and it did this to the file.

I verified in my yarn.lock that I'm on the correct prettier version; I can skip the lint step if you'd prefer and return this to it's normal formatting if y'all are getting different behavior, just let me know.

[uforic]

@kamilogorek - yep, wrote tests, and checks pass. Let me know if you need anything else!

[kamilogorek]

Rebased and merged manually. Thanks!