Add unset method for custom style properties

src/style_manager/view/PropertyView.js

@@ -151,6 +151,7 @@ export default Backbone.View.extend({
   clear(ev) {
     ev && ev.stopPropagation();
     this.model.clearValue();
+    this.__unset();
     // Skip one stack with setTimeout to avoid inconsistencies (eg. visible on padding composite clear)
     setTimeout(() => this.targetUpdated());
   },
@@ -644,6 +645,11 @@ export default Backbone.View.extend({
     this.$input = null;
   },
 
+  __unset() {
+    const unset = this.unset && this.unset.bind(this);
+    unset && unset(this._getClbOpts());
+  },
+
   __update(value) {
     const update = this.update && this.update.bind(this);
     update &&