CreateTable导致panic，建议做错误检查，返回error，直接运行时panic不妥当

[swzry]

`
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x0 pc=0x7509e5]

goroutine 1 [running]:
github.com/aliyun/aliyun-tablestore-go-sdk/tablestore.(*TableStoreClient).CreateTable(0xc000122000, 0xc0000cbeb0, 0x4, 0x4, 0x5)
D:/GoLang/GoWork/src/github.com/aliyun/aliyun-tablestore-go-sdk/tablestore/api.go:348 +0x965
main.CreateTable(0xc000122000, 0x31, 0x84e146)
D:/GoLang/GoWork/src/local_no_vcs/OTSTest202103040238/main.go:42 +0x5ef
main.main()
D:/GoLang/GoWork/src/local_no_vcs/OTSTest202103040238/main.go:17 +0xad
`

相关的上下文（github.com/aliyun/aliyun-tablestore-go-sdk/tablestore/api.go 348行附近）：
`
346 req.ReservedThroughput = new(otsprotocol.ReservedThroughput)
347 req.ReservedThroughput.CapacityUnit = new(otsprotocol.CapacityUnit)
348 req.ReservedThroughput.CapacityUnit.Read = proto.Int32(int32(request.ReservedThroughput.Readcap))
349 req.ReservedThroughput.CapacityUnit.Write = proto.Int32(int32(request.ReservedThroughput.Writecap))

`