Changed line that sets countryCode. Now, when CC is invalid, it is se…

…t to null and therefor not changed

src/components/IntlTelInputApp.js

@@ -719,7 +719,7 @@ class IntlTelInputApp extends Component {
       // invalid dial code, so empty
       // Note: use getNumeric here because the number has not been
       // formatted yet, so could contain bad chars
-      countryCode = '';
+      countryCode = null;
     } else if (!number || number === '+') {
       // empty, or just a plus, so default
       countryCode = this.defaultCountry;