Added parameter checks for NULL values
Added parameter checks for NULL values

rivy/RestSharp,kouweizhong/RestSharp,who/RestSharp,fmmendo/RestSharp,felipegtx/RestSharp,mwereda/RestSharp,wparad/RestSharp,dgreenbean/RestSharp,periface/RestSharp,wparad/RestSharp,RestSharp-resurrected/RestSharp,haithemaraissia/RestSharp,huoxudong125/RestSharp,uQr/RestSharp,mattwalden/RestSharp,KraigM/RestSharp,benfo/RestSharp,PKRoma/RestSharp,SaltyDH/RestSharp,chengxiaole/RestSharp,mattleibow/RestSharp,rucila/RestSharp,cnascimento/RestSharp,amccarter/RestSharp,lydonchandra/RestSharp,jiangzm/RestSharp,restsharp/RestSharp,dmgandini/RestSharp,eamonwoortman/RestSharp.Unity,dyh333/RestSharp