Added comments

Author: ameshkov

packages/tsurlfilter/src/filterlist/rule-storage.ts

@@ -89,14 +89,17 @@ export class RuleStorage {
 
         const list = this.listsMap.get(listId);
         if (!list) {
-            // List doesn't exist
+            // List doesn't exist.
+            //
+            // TODO(ameshkov): Consider throwing an error here.
             return null;
         }
 
         const ruleText = list.retrieveRuleText(ruleIdx);
         if (!ruleText) {
-            list.retrieveRuleText(ruleIdx);
-
+            // The rule could not be found.
+            //
+            // TODO(ameshkov): Consider throwing an error here.
             return null;
         }