Fix a logical bug where Arc4Gen was left in invalid state after a failed

Rekey() call.

Chaos/Cipher/Stream/Arc4/Arc4Gen.hpp

@@ -66,6 +66,8 @@ private:
     template<typename InputIt>
     void RekeyImpl(InputIt keyBegin, InputIt keyEnd)
     {
+        IsInitialized_ = false;
+
         I_ = 0;
         J_ = 0;