return nil when we need a no-op panic handler

cmd/replay/espresso_validation.go

@@ -42,8 +42,5 @@ func handleEspressoPreConditions(message *arbostypes.MessageWithMetadata, isEnab
 			panic("The messaged received by the STF is not an Espresso message, but the validator is running in Espresso mode")
 		}
 	}
-	panicCase := func() {
-		// This no-op allows us to cause no panic in the code that receives the result of this function while keeping the function signature consistent.
-	}
-	return validatingAgainstEspresso, panicCase
+	return validatingAgainstEspresso, nil // return nil for the panic handler such that it is a no-op in the caller if no errors need occur.
 }

cmd/replay/main.go

@@ -327,7 +327,9 @@ func main() {
 
 		} else {
 			// Call the error case closure returned by handleEspressoPreconditions()
-			panicHandler()
+			if panicHandler != nil {
+				panicHandler()
+			}
 		}
 
 		newBlock, _, err = arbos.ProduceBlock(message.Message, message.DelayedMessagesRead, lastBlockHeader, statedb, chainContext, chainConfig, batchFetcher, false)