Revert "remove assertion (#289)"
Revert "remove assertion (#289)"

This reverts commit ae9e8cdce428b4584bb04371a7bc51d0c1ca1e64.

rsocket/rsocket-cpp,phoad/rsocket-cpp,alexmalyshev/rsocket-cpp,vjn/reactivesocket-cpp,vjn/rsocket-cpp,alexmalyshev/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,alexmalyshev/rsocket-cpp,vjn/reactivesocket-cpp,alexmalyshev/rsocket-cpp,vjn/rsocket-cpp,vjn/reactivesocket-cpp,phoad/rsocket-cpp,vjn/rsocket-cpp,phoad/rsocket-cpp,phoad/rsocket-cpp,rsocket/rsocket-cpp,ReactiveSocket/reactivesocket-cpp,rsocket/rsocket-cpp,phoad/rsocket-cpp,rsocket/rsocket-cpp,ReactiveSocket/reactivesocket-cpp