Guard against nil in Parity.Trace.Action input

Fixes #1115

apps/ethereum_jsonrpc/lib/ethereum_jsonrpc/parity/trace/action.ex

@@ -44,8 +44,8 @@ defmodule EthereumJSONRPC.Parity.Trace.Action do
     Enum.into(action, %{}, &entry_to_elixir/1)
   end
 
-  defp entry_to_elixir({key, _} = entry)
+  defp entry_to_elixir({key, value} = entry)
-       when key in ~w(address callType from init input refundAddress to),
+       when key in ~w(address callType from init input refundAddress to) and is_binary(value),
        do: entry
 
   defp entry_to_elixir({key, quantity}) when key in ~w(balance gas value) do