advapi32: Fix potential NULL pointer dereference in RegSetValueExA [with test] (Saturn)

[Aurimas Fišeras]

Alexandre Julliard wrote:
> Aurimas Fišeras <aurimas at gmail.com> writes:
> 
>> Alexandre Julliard wrote:
>>> Of course Windows has exception handlers all over the place, but that
>>> doesn't mean we want to replicate that behavior.
>> But we want to have a "bug-for-bug" compatibility with Windows?
>> Without this patch windows just returns an error, while wine crashes.
> 
> We only want it when an actual app depends on it, otherwise we'd have to
> add exception handlers in all functions. Note that the Windows behavior
> often varies across versions too.
> 
So why are we fixing various "Possible NULL pointer dereference" errors
reported by Coverity?