EXT SuperBoxSelect使用 所在FormPanel销毁问题

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initComponent:function() {
       Ext.apply(this, {
            items           : new Ext.util.MixedCollection(false),
            usedRecords     : new Ext.util.MixedCollection(false),
            addedRecords    : [],
            remoteLookup    : [],
            hideTrigger     : true,
            grow            : false,
            resizable       : false,
            multiSelectMode : false,
            preRenderValue  : null
        });
        
        if(this.transform){
            this.doTransform();
        }
    
        if(this.forceFormValue){
            this.items.on({
               add: this.manageNameAttribute,
               remove: this.manageNameAttribute,
               clear: this.manageNameAttribute,
               scope: this
            })
        }
        
        Ext.ux.form.SuperBoxSelect.superclass.initComponent.call(this);
        if(this.mode === 'remote' && this.store){
            this.store.on('load', this.onStoreLoad, this);
        }
       this.on('beforedestroy', function(){// 添加被销毁前事件
            this.clearValue(true);
        })
},
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