Some event handler converts to boolean

[abnerlee]

Hi,

const h = (tag, props, ...children) => ({ tag, props, children });
const html = htm.bind(h);
const dom = html`<div onCompositionStart=${()=>{}} onClick=${()=>{}}>aaa</div>`

In props, the onCompositionStart becomes true. The expected behavior is that the value of onCompositionStart and onClick in props should both be Function