fix wrong zones property, causing correct $zones array accumulation (#5828)

Author: mkslanc

src/ext/diff/base_diff_view.js

@@ -346,14 +346,14 @@ class BaseDiffView {
             if (!this.activeEditor) {
                 return;
             }
-            this.activeEditor.renderer.$scrollDecorator.zones = [];
+            this.activeEditor.renderer.$scrollDecorator.$zones = [];
         }
         else {
             if (!this.editorA || !this.editorB) {
                 return;
             }
-            this.editorA.renderer.$scrollDecorator.zones = [];
-            this.editorB.renderer.$scrollDecorator.zones = [];
+            this.editorA.renderer.$scrollDecorator.$zones = [];
+            this.editorB.renderer.$scrollDecorator.$zones = [];
         }
 
         /**