Error-handling in AIO happens mainly in two places:
1. For errors happening inside the app we have a custom `ErrorHandler`
implementation, `ReportingErrorHandler`. `ReportingErrorHandler`
passes errors to the default `ErrorHandler` (for them to be logged to
the console) and also forwards them to `window.onerror()`.
2. Errors happening outside the app and errors forwarded by
`ReportingErrorHandler` are handled by `window.onerror()`, which in
turn reports them to Google analytics.
Previously, we were making some assumptions (which turned out to be
incorrect based on the info captured in Google analytics - see #28106):
- `ReportingErrorHandler` assumed that the errors passed to its
`handleError()` method would be either strings or `Error` instances.
_Apparently, other values (such as `null` or `undefined`) may also be
passed._
- `window.onerror()` assumed that if an `Error` instance was passed in,
it would always have a stacktrace (i.e. its `stack` property would be
defined).
_This is not necessarily true, although it is not clear (based on the
logs) whether reported errors of this type are caused by `Error`
instance with no stacktrace or by non-string error objects which are
incorrectly treated as `Error` instances.
This commit ensures that all types of error arguments can be handled
correctly, including `Error` instances with no stacktrace and other
types of objects or primitives.
NOTE:
PR #42881 is related as it fixes handling `null` and `undefined`
arguments in the default `ErrorHandler`.
Fixes#28106
PR Close#42883
e7c770709b