TabSet.addAddTabClickedHandler warning

[Hirn]

I want to use the add button in TabSet but I get a warning by click addButton
my source

TabSet templatesTabSet = new TabSet();
        templatesTabSet.setCanAddTabs(true);
        templatesTabSet.addAddTabClickedHandler(new AddTabClickedHandler() {
            @Override
            public void onAddTabClicked(AddTabClickedEvent event) {
                SC.askforValue(Strings.get("addTemplatesList"), Strings.get("templatesListName"), new ValueCallback() {
                    @Override
                    public void execute(String value) {
                          int i = 0;
                    }
                });
            }
        });

WARN:Log:Call to Super for method: addTabClicked failed on: [ImgButton ID:isc_TabSet_0_addTabButton]: couldn't find a superclass implementation of : ImgButton.addTabClicked
    [c]Class.invokeSuper(_1=>null, _2=>"addTabClicked", _3=>undef, _4=>undef, _5=>undef, _6=>undef, _7=>undef, _8=>undef, _9=>undef, _10=>undef, _11=>undef, _12=>undef, _13=>undef) on [ImgButton ID:isc_TabSet_0_addTabButton] @ ISC_Core.js:319:219
    [c]Class.Super(_1=>"addTabClicked", _2=>[object Arguments], _3=>undef) on [ImgButton ID:isc_TabSet_0_addTabButton] @ ISC_Core.js:312:170
    _3.<anonymous>() on [ImgButton ID:isc_TabSet_0_addTabButton] @ 282C42893C7CFAE7A1483F825C7B3C33.cache.js:227198:12
    null.dsc_g$(jsFunction_0_g$=>anonymous(), thisObj_0_g$=>[ImgButton ID:isc_TabSet_0_addTabButton], args_0_g$=>[object Arguments]) @ 282C42893C7CFAE7A1483F825C7B3C33.cache.js:65393:28
    null.gsc_g$(jsFunction_0_g$=>anonymous(), thisObj_0_g$=>[ImgButton ID:isc_TabSet_0_addTabButton], args_0_g$=>[object Arguments]) @ 282C42893C7CFAE7A1483F825C7B3C33.cache.js:65449:16
    _3.<anonymous>() on [ImgButton ID:isc_TabSet_0_addTabButton] @ 282C42893C7CFAE7A1483F825C7B3C33.cache.js:65429:14
    StatefulCanvas.handleActivate(_1=>Obj, _2=>undef) on [ImgButton ID:isc_TabSet_0_addTabButton] @ ISC_Foundation.js:239:73
    StatefulCanvas.handleClick(_1=>Obj, _2=>undef) on [ImgButton ID:isc_TabSet_0_addTabButton] @ ISC_Foundation.js:240:13
    [c]EventHandler.bubbleEvent(_1=>[ImgButton ID:isc_TabSet_0_addTabButton], _2=>"click", _3=>undef, _4=>undef, _5=>undef) on [Class EventHandler] @ ISC_Core.js:2449:89
    [c]EventHandler.handleClick(_1=>[ImgButton ID:isc_TabSet_0_addTabButton], _2=>undef) on [Class EventHandler] @ ISC_Core.js:2281:50
    EventHandler._handleMouseUp(_1=>[object MouseEvent], _2=>undef) on [Class EventHandler] @ ISC_Core.js:2263:11
    [c]EventHandler.handleMouseUp(_1=>[object MouseEvent], _2=>undef) on [Class EventHandler] @ ISC_Core.js:2254:57
    [c]EventHandler.dispatch(_1=>[c]EventHandler.handleMouseUp(), _2=>[object MouseEvent]) on [Class EventHandler] @ ISC_Core.js:2544:122
    HTMLDocument.eval(event=>[object MouseEvent]) @ [no file]:3:123

despite the warning, the event handler is triggered.

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