Fix Sentry error processing for errors missing a stack

[Gudahtt]

Errors without stack traces would break the Sentry error processing, which assumes the presence of a stack trace. Many errors don't have any stack trace though, such as uncaught promises.

This breakage resulting in the app state being missing from the error report, and a console warning.

[metamaskbot]

Builds ready [566e19a]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (671 ± 69 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Notification	firstPaint	36	111	51	20	10
		domContentLoaded	374	861	670	143	69
		load	375	863	671	143	69
		domInteractive	374	861	669	143	69

[whymarrh]

Could we use options chaining here?

[Gudahtt]

I'm not sure how optional chaining applies 😕 This line isn't an assignment - it's looping through and mutating the array.

[whymarrh]

item.stacktrace?.frames

Instead of adding the check for stacktrace, we could use ?.

[Gudahtt]

Ah right - it hadn't occurred to me to use optional chaining in the case where you aren't using the return value. Sure, I can update this.

[Gudahtt]

Unfortunately using optional chaining without capturing the result in a variable triggers the no-unused-expressions eslint rule, due to this bug. I'd rather leave this as-is for now rather than add an ignore comment.