Ensure selectors in CssRule

src/css_composer/model/CssRule.js

@@ -55,12 +55,18 @@ export default Backbone.Model.extend(Styleable).extend({
 
   ensureSelectors() {
     const { em } = this;
-    const result = [];
     const sm = em && em.get('SelectorManager');
-    const selectors = this.getSelectors();
-    const toInit = Array.isArray(selectors);
-    selectors.forEach(sel => result.push(sm ? sm.add(sel) : sel));
-    toInit && this.set('selectors', new Selectors(result));
+    const toListen = [this, 'change:selectors', this.ensureSelectors];
+    let sels = this.getSelectors();
+    this.stopListening(...toListen);
+
+    if (Array.isArray(sels)) {
+      const res = sels.filter(i => i).map(i => (sm ? sm.add(i) : i));
+      sels = new Selectors(res);
+    }
+
+    this.set('selectors', sels);
+    this.listenTo(...toListen);
   },
 
   /**