riched20: new selection invalidation logic

[Krzysztof Foltman]

Vitaliy Margolen wrote:

> upset. Users will have their functioning installers and you will have your error
> reports.

I will have my error reports? How exactly will I get them? Does average 
user (or Wine) send us err: error reports? If he/she usually had, this 
would be a non-issue, and asserts could be replaced with if (!condition) 
ERR(...).

Krzysztof