[nfsfile] fix arg type mismatch

Fixes coverity CID 1250595
[smbfile] fix arg type mismatch

Fixes coverity CID 1250592/1250595
[rendermanager] fix possible null ptr dereference in CXBMCRenderManager::GetOptimalBufferSize()

Fixes coverity CID 1243594
[vaapi] fix missing break in switch