[WindowFrame] Ensure we call Backend.Initialize before anything happen on it
[WindowFrame] Ensure we call Backend.Initialize before anything happen on it

Previously, base.OnBackendCreated could be trying to register event on the backend if the right method was overloaded causing a NRE

hamekoz/xwt,mminns/xwt,directhex/xwt,lytico/xwt,antmicro/xwt,residuum/xwt,hwthomas/xwt,mminns/xwt,sevoku/xwt,TheBrainTech/xwt,steffenWi/xwt,iainx/xwt,cra0zy/xwt,akrisiun/xwt,mono/xwt