Added check if sourcify integration is enabled

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Features
 
 ### Fixes
+- [#4388](https://github.com/blockscout/blockscout/pull/4388) - Fix internal server error on contract page for insctances without sourcify envs
 
 ### Chore
 - [#4382](https://github.com/blockscout/blockscout/pull/4382) - Replace awesomplete with autocomplete.js

apps/block_scout_web/lib/block_scout_web/controllers/address_contract_verification_controller.ex

@@ -275,6 +275,7 @@ defmodule BlockScoutWeb.AddressContractVerificationController do
     if Chain.smart_contract_fully_verified?(address_hash_string) do
       {:ok, :already_fully_verified}
     else
+      if Application.get_env(:explorer, Explorer.ThirdPartyIntegrations.Sourcify)[:enabled] do
         if Chain.smart_contract_verified?(address_hash_string) do
           case Sourcify.check_by_address(address_hash_string) do
             {:ok, _verified_status} ->
@@ -295,6 +296,9 @@ defmodule BlockScoutWeb.AddressContractVerificationController do
               {:error, :not_verified}
           end
         end
+      else
+        {:error, :sourcify_disabled}
+      end
     end
   end
 end