[UEPR-386] Sound editor crashes

[adzhindzhi]

Resolves

UEPR-386

Proposed Changes

• Check if a sound with the provided index exists before trying to access its data

Reason for Changes

• This issue became visible after the React 18 upgrade. After a sound is removed for the first time, mapStateToProps is not re-evaluated, so no error occurs. On subsequent deletions, however, mapStateToProps is re-run via handleSubsequentCalls, which ends up calling getSoundBuffer when this.editingTarget.sprite.sounds[soundIndex] is already empty. This bug existed before React 18, but my assumption is that the previous React-Redux implementation swallowed errors thrown inside mapStateToProps, preventing them from surfacing. With React 18 errors thrown during render are no longer suppressed and now propagate, which is why the editor crashes after the upgrade even though the underlying bug was always present.

[KManolov3]

Thanks for catching this so quickly!