Throw error if invalid language is selected

src/settingsManager.ts

@@ -78,6 +78,10 @@ export interface Settings {
 export const setLanguage = (selectedLanguage: string, i18n: any) => {
   // Locales and languages in arrays to match them
   const locale = locales[languages.indexOf(selectedLanguage)]
+
+  if (!locale) {
+    throw Error("Error while setting locale, " + selectedLanguage + " does not exist.")
+  }
   localStorage.setItem('language', locale)
   i18n.locale = locale
 }