[Bug 27106] IMSSA EuroDEEM (VB6 app) fails on startup, reporting "Type MisMatch" error (VARIANT_Coerce: treat VT_NULL like VT_EMPTY when converting to VT_BSTR)

https://bugs.winehq.org/show_bug.cgi?id=27106

--- Comment #6 from Nikolay Sivov  ---
(In reply to comment #4)
> __vbaVarCat: left=VT_DISPATCH, right=VT_BSTR
>
> IDispatch_Invoke() succeeds and returns VT_NULL type for default 'value'
> property (see MSDATL3 calls which happen during IDispatch invoke).
>
> The problem is the conversion to VT_BSTR.
>
> VARIANT_FromDisp() -> VariantChangeTypeEx() -> VARIANT_Coerce()
>
> Wine doesn't handle the case VT_NULL -> VT_BSTR properly, leading to
> conversion failure (DISP_E_TYPEMISMATCH).

Apparently we have some tests for that, and it should actually fail as it does
now. It seems to me that a problem is in VARIANT_FromDisp(), vartype.c has a
comment about some complication to test it.