What I am trying to do is, have multiple buttons to create different elements. The title is the error message that appear in my console when i run my app.

This is my codesandbox link that shows the code and error. Click on the link and open the console, the error is there

create chart function

 onChartItem() {
    /*eslint no-console: 0*/
    console.log("adding", "n" + this.state.newCounter);
    this.setState({
      // Add a new item. It must have a unique key!
      charts: this.state.charts.concat({
        i: "n" + this.state.newCounter,
        x: (this.state.charts.length * 2) % (this.state.cols || 12),
        y: Infinity, // puts it at the bottom
        w: 8,
        h: 6
      }),
      // Increment the counter to ensure key is always unique.
      newCounter: this.state.newCounter + 1
    });
  }

any advice is appreciated