Current behavior: React Devtools throws "RangError: Invalid Array Length" when integers are used as keys on react elements. 

Example: 

https://codesandbox.io/s/interesting-violet-v5c5j

https://v5c5j.csb.app/

Using anything but strings as keys is as far as I understand not even correct usage, but it would be great if react devtools checked a little bit earlier and had a nicer error than "RangeError: Invalid Array Length." It takes a long time to figure out from this message that one somehow managed to use integers as keys and needs to correct it.

I've only tested with Chrome and the latest version of react devtools as a chrome extension. 
<Parent count={count} />
        </React.Fragment>
      );
      const Parent = ({count}) =>
        new Array(count).fill(true).map((_, index) => <Child key={index} />);
      const Child = () => <div>Hi!</div>;
      act(() =>
        ReactDOM.render(
          <Grandparent count={2} />,
          document.createElement('div'),
        ),
      );
      expect(store).toMatchSnapshot('1: mount');
      const grandparentID = store.getElementIDAtIndex(0);
      act(() => store.toggleIsCollapsed(grandparentID, false));
      expect(store).toMatchSnapshot('2: expand Grandparent');
      const parentOneID = store.getElementIDAtIndex(1);
      const parentTwoID = store.getElementIDAtIndex(2);
      act(() => store.toggleIsCollapsed(parentOneID, false));
      expect(store).toMatchSnapshot('3: expand first Parent');
      act(() => store.toggleIsCollapsed(parentTwoID, false));
      expect(store).toMatchSnapshot('4: expand second Parent');
      act(() => store.toggleIsCollapsed(parentOneID, true));
      expect(store).toMatchSnapshot('5: collapse first Parent');
      act(() => store.toggleIsCollapsed(parentTwoID, true));
      expect(store).toMatchSnapshot('6: collapse second Parent');
      act(() => store.toggleIsCollapsed(grandparentID, true));
      expect(store).toMatchSnapshot('7: collapse Grandparent');
    });
    it('should support expanding deep parts of the tree', () => {