Restore suggested languages to compact languages button

The filterForCommonLanguagesForUser method checks if commonInterlanguageList
is null, but it can never be null unless it is first initialized that
way.

Bug: T282037
Change-Id: I70c3a60349693473509d9b329764dc5138930506

resources/js/ext.uls.launch.js

@@ -3,7 +3,7 @@
  */
 
 /* eslint-disable no-implicit-globals */
-var commonInterlanguageList;
+var commonInterlanguageList = null;
 
 /**
  * @param {string[]} languageCodes array of language codes available