fix(lang): fixed initial language

src/features/AuthServiceApp/index.tsx

@@ -17,7 +17,7 @@ setClientTitleAndDescription(client.title, client.description)
 setClientIcons(client.name)
 
 const Background = client.background
-const initialLanguage = getLanguageUrlParam() || client.defaultLanguage
+const initialLanguage = getLanguageUrlParam()
 
 const AuthServiceApp = () => (
   <BrowserRouter>

src/helpers/languageUrlParam/index.tsx

@@ -1,10 +1,13 @@
+import isNull from 'lodash/isNull'
+
 import { history } from 'config/history'
+import { client } from 'config/clients'
 
 const KEY = 'lang'
 
 export const getLanguageUrlParam = () => {
   const lang = new URLSearchParams(history.location.search).get(KEY)
-  return lang || undefined
+  return (lang !== 'null' && !isNull(lang)) ? lang : client.defaultLanguage
 }
 
 export const addLanguageUrlParam = (lang: string, url: string) => {