Fix crash in issue 3845 and defects B/C in 3779

[softins]

Short description of changes

This PR implements the two fixes listed by LLM in #3845, one of which is also Defect C listed in #3779 (comment)

It also fixes Defect B from #3779 (comment) by adding try/catch blocks around sound card initialization. This corrects the crash I observed when testing just the fixes in #3845. Exceptions should not be allowed to escape from slot functions in Qt.

CHANGELOG: Client: Avoid crashing on sound device errors.

Context: Fixes an issue?

Fixes #3845 and part of #3779 (but not the ASIO parts).

Does this change need documentation? What needs to be documented and how?

Bugfix, so probably not.

Status of this Pull Request

Ready for test.

What is missing until this pull request can be merged?

Review

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above

[mcfnord]

MY LLM WROTE:

Measured this PR on the real cross-thread path: client on jackd, then stop jackd → the CGenErr from OnSndCrdReinitRequest. x86 / Qt 5.15.13, offscreen, 5 trials each.

stderr signal	baseline fa8766ad	this PR
Qt has caught an exception… (escaped the slot)	5/5	0/5
QMutex: destroying locked mutex	5/5	0/5

A build with a print inside your catch fired 5/5 on the same path — so the throw still happens and is now contained at the slot, not skipped. QMutexLocker removes the leaked mutex.

I could not reproduce the Raspberry Pi hard abort in six earlier configs, and don't here (no Windows hardware either), so I'm not validating the ASIO/RPi terminate directly — but the escape mechanism behind Defect C / #3845 is gone in every trial.

[pljones]

Merged to main and backported to release/3_12.