Issue #804

<img 
    src={user.avatarUrl} 
    onError={(e) => {
        e.target.onerror = null; 
        e.target.src = "/images/default.png"
    }}
/>

Extract to React Component

interface Props {
    src: string
    className: string
    fallback: string
}

export default function FallbackImg(props: Props) {
    return (
        <img className={props.className} 
            src={props.src} 
            onError={(e) => {
                // @ts-ignore
                e.target.src = props.fallback
        }} />
    )
}

How to fallback backgroundImage

Use 2 url

var el = document.createElement('div')
 el.className = 'marker'
el.style.backgroundImage = `url('${user.avatarUrl}'), url('/images/user.png')`