Do not crash on UTF-8 decode errors

[kubouch]

• [] I have added an entry to CHANGELOG.md, or an entry is not needed for this change

Summary of changes

This PR implements a fix suggested in https://github.com/cs01/gdbgui/issues/407.

There are also other UTF-8 issues that might be related to this: https://github.com/cs01/gdbgui/issues/130 https://github.com/cs01/gdbgui/issues/347 https://github.com/cs01/gdbgui/issues/292

Test plan

Tested by running

# command(s) to exercise these changes

[kubouch]

I haven't actually tested the changes yet but I can try later when I have more time.

[cs01]

This looks good, will merge if it's tested

[AuroransSolis]

Tested it out here on a program that had been causing gdbgui to crash for me and it seems to be working well. Can provide source if necessary, but I'm unsure if the same error will crop up on other machines.

[kubouch]

Sorry, I moved to other projects and haven't used gdbgui or even gdb since, I don't have a reproduction example anymore.

[AuroransSolis]

I meant that I can provide the source to reproduce the issue. Your patch did work very well on my machine, at least, so it has that going for it.

[kubouch]

You can paste the source here.

[cs01]

Thank you!