Fix toLocalString language key - Fixes #13255 (#13295)

* Finish localizeNumber ctch null
- Incomplete null catch: accidentally called string replace on an array
- Call lang resolution on array just incase service is passing valid lang array
(linting hasn't been checked)

* Got my local linter working

website/client/src/filters/localizeNumber.js

@@ -1,7 +1,21 @@
+// Lang resolution (passed into replace)
+const langRes = [
+  // Strip beyond @ symbol to allow custom languages
+  [/@(?:.+)$/, ''],
+  // We use underscore, this mthd uses dash
+  ['_', '-'],
+];
+
+// Lang resolution reducer
+const langReduce = (str, params) => str.replace(...params);
+
 export default function localizeNumber (valIn, lang, optIn = {}) {
   // Extra catch just incase non number
   const val = (typeof valIn === 'number') ? valIn : parseFloat(valIn);
 
+  // Catch lang null
+  const langCatch = (lang || []);
+
   // Options Management
   const { toFixed } = optIn;
   const optOut = {};
@@ -11,12 +25,11 @@ export default function localizeNumber (valIn, lang, optIn = {}) {
   }
 
   return val.toLocaleString(
-    // Catch null just incase
-    (lang || [])
-      // Strip beyond @ symbol to allow custom languages
-      .replace(/@(?:.+)$/, '')
-      // We use underscore, this mthd uses dash
-      .replace('_', '-'),
+    langCatch instanceof Array
+      // Must use map with array
+      ? langCatch.map(each => langRes.reduce(langReduce, each))
+      // Parse to string as final backup
+      : langRes.reduce(langReduce, langCatch.toString()),
     optOut,
   );
 }