Throw exception if site store isnt found in SiteBasedRequestResolver

[pascalheidmann]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	#...

If you have a custom resolver with a priority lower than SiteBasedRequestResolver and are inside a request flagged as site request it will never come so far as it will return null instead of erroring

[CLAassistant]

All committers have signed the CLA.

[dpfaffenbauer]

I am not really sure about potential BC breaks, maybe others suspect that the default store is returned when there is no store for the site

[pascalheidmann]

@dpfaffenbauer returning the default store would be also a valid solution for me (which errors if none found). But at least it should not fail silently/break the resolver which expects a valid store and not null

[dpfaffenbauer]

@pascalheidmann I think we should do it. At least within 3.x

[dpfaffenbauer]

thanks @pascalheidmann