Update part2e.md

translated a finnish part in embedded code sample
and the initial value of currency was null
```
const App = () => {
  const [value, setValue] = useState('')
  const [rates, setRates] = useState({})
  const [currency, setCurrency] = useState(null)
```

Author: hbaklan943

src/content/2/en/part2e.md

@@ -550,11 +550,11 @@ The effect has the following condition
 
 ```js
 if (currency) { 
-  // haetaan valuuttakurssit
+  // exchange rates are fetched
 }
 ```
 
-which prevents requesting the exchange rates just after the first render when the variable _currency_ still has the initial value, i.e. an empty string.
+which prevents requesting the exchange rates just after the first render when the variable _currency_ still has the initial value, i.e. a null value.
 
 So if the user writes e.g. <i>eur</i> in the search field, the application uses Axios to perform an HTTP GET request to the address https://open.er-api.com/v6/latest/eur and stores the response in the _rates_ state.