Dockable LeftNav

AppNav.js

class AppNav extends React.Component {
    componentWillReceiveProps(nextProps) {
        if (this.props.fixed !== nextProps.fixed) {
            if (nextProps.fixed) {
                this.refs.nav.open();
            } else {
                this.refs.nav.close();
            }
        }
    }

    open() {
        this.refs.nav.open();
    }

    render() {
        const outerStyle = {
            position: (this.props.fixed) ? "relative" : undefined,
            width: (this.props.fixed) ? 256 : undefined,
            flexShrink: 0
        };
        const style = {};
        if (this.props.fixed) {
            style.position = "absolute";
        }
        return (
            <div style={outerStyle}>
                <mui.LeftNav ref="nav"
                             docked={this.props.fixed}
                             menuItems={this.props.menuItems}
                             selectedIndex={this.props.selectedIndex}
                             style={style}
                             onChange={this.props.onNavigate} />
            </div>
        );
    }
}

This component assumes it's nested in a flexbox container.

which part should I change if I didn't wrap it in a flexbox container
I only use flexbox on smaller component.