fix #2464

src/js/static-net-filtering.js

@@ -978,6 +978,12 @@ var FilterHostnameDict = function() {
     this.dict = new Set();
 };
 
+Object.defineProperty(FilterHostnameDict.prototype, 'size', {
+    get: function() {
+        return this.dict.size;
+    }
+});
+
 FilterHostnameDict.prototype.add = function(hn) {
     if ( this.dict.has(hn) ) {
         return false;
@@ -986,6 +992,10 @@ FilterHostnameDict.prototype.add = function(hn) {
     return true;
 };
 
+FilterHostnameDict.prototype.remove = function(hn) {
+    return this.dict.delete(hn);
+};
+
 FilterHostnameDict.prototype.match = function() {
     // TODO: mind IP addresses
     var pos,
@@ -2097,8 +2107,8 @@ FilterContainer.prototype.removeBadFilters = function() {
             continue;
         }
         if ( entry instanceof FilterHostnameDict ) {
-            entry.delete(fclass);  // 'fclass' is hostname
-            if ( entry.dict.size === 0 ) {
+            entry.remove(fclass);  // 'fclass' is hostname
+            if ( entry.size === 0 ) {
                 this.categories.delete(hash);
             }
             continue;