Revoke URLs of loaded icons

Closes #13095
(grafted from ee2fee1a4b3019a5e4bff38e830a751d9c4d0976)

--HG--
branch : 6.0

sao/src/common.js

@@ -2935,11 +2935,8 @@
         load_icons: function(refresh) {
             refresh = refresh || false;
             if (!refresh) {
-                for (var icon_name in this.load_icons) {
-                    if (!this.load_icons.hasOwnProperty(icon_name)) {
-                        continue;
-                    }
-                    window.URL.revokeObjectURL(this.load_icons[icon_name]);
+                for (var icon_name in this.loaded_icons) {
+                    window.URL.revokeObjectURL(this.loaded_icons[icon_name]);
                 }
             }