Uncaught TypeError: r.current.contains is not a function in kendo DriopDownList

While working with Kendo React, I wanted to add a Kendo DropDownList. I tried to fill the list with data like this:

Array(8) [ {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…} ]
​
0: Object { id: -1, name: null }
​
1: Object { id: 1, name: "A" }
​
2: Object { id: 2, name: "B" }
​
3: Object { id: 3, name: "C" }
​
4: Object { id: 4, name: "D" }
​
5: Object { id: 5, name: "E" }
​
6: Object { id: 6, name: "F" }
​
7: Object { id: 77, name: "G" }

The data is fetched with axios and put inside useState in UseEffect:

const[sektor, setSektor] = useState([]);
...
...
useEffect(() => {   
      (async() =>{
        try{
          const resSektor = await services.getSektor();
          console.log(resSektor.data.rlista); //JSON above is this console log
          setSektor(resSektor.data.rlista);
        }
        catch(e){
          console.log(e);
        }
      })();
     
       }, []);

So, 'sektor' is used as an array of objects that will fill the Kendo dropdown:

<DropDownList data={sektor} value={sektorV} style={{marginTop:'2%'}} onChange={handleChangeSektor} textField="name" dataItemKey="id"/>
...
...
const handleChangeSektor = (event) => {
      setSektorV(event.target.value);
    };

'sektorV' is a state that saves the object that is picked from the KendoDropDown and is defined like this:

const[sektorV, setSektorV] = useState({id: -1, name: "All"});

Everything seems to be correct, but when I click on the DropDown the screen goes white and this is console logged:

Uncaught TypeError: r.current.contains is not a function
...
Uncaught TypeError: _utils__WEBPACK_IMPORTED_MODULE_2__.getItemValue(...) is null

I had a bunch of dropdowns in my current project and they all worked fine. Can anybody see the problem?

Just a hunch based on this limited code context, but I think this error is thrown because the first element has a null name property in the resSektor.data.rlista array.

Try setSektor(resSektor.data.rlista.slice(1)); to remove the null value or instead of null update that element's name property to "ALL" to match the initial sectorV state.

useEffect(() => {   
  (async() =>{
    try {
      const resSektor = await services.getSektor();
      resSektor.data.rlista[0].name = "All";
      setSektor(resSektor.data.rlista);
    } catch(e) {
      console.log(e);
    }
  })();
}, []);