Detecting an invalid handle in setupapi

[Paul Vriens]

Hi,

I'm trying to install Microsoft's MMC (W2K3) and it crashes every now 
and then with different symptoms.

I've tracked it down to what I think is a fault in the application that 
triggers a bug in Wine. All inf files that are read are closed with 
SetupCloseInfFile but the app is still trying to use the handle in a 
call to SetupFindFirstLineA.

On Windows (tested on W2K3) this will lead to a failure of 
SetupFindFirstLineA with a last error of ERROR_INVALID_HANDLE. On Wine 
we don't check the handle and thus the outcome cannot be predicted 
(mostly crash).

What ways do we have to detect invalid handles or better yet how can 
this be solved?