Forgot to make 404 not found page

[ChaoTzuJung]

If I type wrong url, I will git error on page
EX:
http://localhost:3000/palette/&@#$%%

react-colors/colors-app/src/App.js

Lines 21 to 25 in c358775

	findPalette(id) {
	return this.state.palettes.find(function(palette) {
	return palette.id === id;
	});
	}

Maybe it could write this to fix issue

  findPalette = id => {
    const defaultPalette = colorsConfig[0];
    return this.state.palettes.find(palette => palette.id === id) || defaultPalette;
  }