message: Skip null or undefined children in vdom
diff: @@ -11,8 +11,10 @@ const ATTR_PROPS = '_props';
  export const createElement = (tag: string | Function, props: {}, ...children) => {
  let ch = [];
  const push = (c) => {
  + if (c !== null && c !== undefined) {
  ch.push((typeof c === 'function' || typeof c === 'object') ? c : `${c}`);
  }
  + }
  children.forEach(c => {
  if (Array.isArray(c)) {
  c.forEach(i => push(i));
  