fix CR issue

apps/ethereum_jsonrpc/lib/ethereum_jsonrpc/rolling_window.ex

@@ -209,12 +209,14 @@ defmodule EthereumJSONRPC.RollingWindow do
   @doc """
   Display the raw contents of all windows for a given key.
   """
-  @spec inspect(table :: atom, key :: term()) :: nonempty_list(non_neg_integer)
+  @spec inspect(table :: atom, key :: term()) :: nonempty_list(non_neg_integer) || []
   def inspect(table, key) do
-    if :ets.whereis(table) == :undefined do
+    case :ets.whereis(table) do
+      :undefined ->
         []
-    else
-      case :ets.lookup(table, key) do
+
+      tid ->
+        case :ets.lookup(tid, key) do
           [{_, current_window, windows}] ->
             [current_window | windows]