XWIKI-15140: Allow giving a chain of translations keys fallbacks to the localization script service

xwiki-platform-core/xwiki-platform-localization/xwiki-platform-localization-script/src/main/java/org/xwiki/localization/script/LocalizationScriptService.java

@@ -394,7 +394,13 @@ public String render(Collection<String> keys, Syntax syntax, Collection<?> param
                 result = null;
             }
         } else {
-            result = keys.iterator().next();
+            result = null;
+
+            for (String key : keys) {
+                if (key != null) {
+                    result = key;
+                }
+            }
         }
 
         return result;