ios: use a default error text instead of crashing

[markusfisch]

Because e.what() returns nil sometimes, what is causing a crash when initializing the dictionary.

[axxel]

Do you see any chance to reproduce the issue? According to https://stackoverflow.com/a/1038504 e.what() can only return nullptr if a custom class returns that (or the iOS stdlib implementation is buggy). If there is an issue we can fix somewhere in the writer implementation, I'd prefer that.

[markusfisch]

No, unfortunately we don't have a sample or any more info 🤷‍♂️ But we're seeing this crash happening to our users in our crash logging system.

[axxel]

I checked all throw statements and this looks like a bug in the libc++ implementation on iOS. weird.

[axxel]

It is so nice if unrelated compilation issues (see recent wasm build failures) that randomly show up can also randomly disappear again... ;)

[markusfisch]

Well, in my experience, such random issues unfortunately always come back 😉

(And I was wondering about the wasm build failures already, too).