[PATCH setup] Ignore reinstall requests if version is not accessible

[Jon Turney]

On 11/12/2022 15:11, Christian Franke via Cygwin-apps wrote:
> This prevents accidental package loss if reinstall is run from local 
> directory but the package is no longer cached.

Thanks.  This seems right, so please apply.

> Possible further improvement: Do not offer "Reinstall" in the popup menu 
> in this case.

Indeed.

That might be simply fixable, but really, we need to keep an index of 
the files in the package cache, so we can handle situations like this 
properly, without spending lots of time spinning rust (we could then 
also do some expiry on the cache, which is a feature that has been 
needed for decades...)