Check ets table exists for know tokens

CHANGELOG.md

@@ -9,6 +9,7 @@
 
 
 ### Fixes
+- [#3382](https://github.com/poanetwork/blockscout/pull/3382) - Check ets table exists for know tokens
 - [#3376](https://github.com/poanetwork/blockscout/pull/3376) - Fix contract nested inputs
 - [#3375](https://github.com/poanetwork/blockscout/pull/3375) - Prevent terminating of tokens/contracts process
 - [#3374](https://github.com/poanetwork/blockscout/pull/3374) - Fix find block timestamp query

apps/explorer/lib/explorer/known_tokens/known_tokens.ex

@@ -94,13 +94,21 @@ defmodule Explorer.KnownTokens do
   @spec lookup(String.t()) :: {:ok, Hash.Address.t()} | :error | nil
   def lookup(symbol) do
     if store() == :ets && enabled?() do
+      if ets_table_exists?(table_name()) do
         case :ets.lookup(table_name(), symbol) do
           [{_symbol, address} | _] -> Hash.Address.cast(address)
           _ -> nil
         end
+      else
+        nil
+      end
     end
   end
 
+  defp ets_table_exists?(table) do
+    :ets.whereis(table) !== :undefined
+  end
+
   @doc false
   @spec table_name() :: atom()
   def table_name do