Use Array.Empty in benchmark when response size is zero (#1819)

Author: JamesNK

perf/benchmarkapps/Shared/BenchmarkServiceImpl.cs

@@ -92,7 +92,8 @@ public override async Task StreamingBothWays(IAsyncStreamReader<SimpleRequest> r
 
     public static SimpleResponse CreateResponse(SimpleRequest request)
     {
-        var body = UnsafeByteOperations.UnsafeWrap(new byte[request.ResponseSize]);
+        var data = request.ResponseSize == 0 ? Array.Empty<byte>() : new byte[request.ResponseSize];
+        var body = UnsafeByteOperations.UnsafeWrap(data);
 
         var payload = new Payload { Body = body };
         return new SimpleResponse { Payload = payload };