message: Set lightTheme as default ThemeContext value
diff: @@ -3,13 +3,14 @@ import React from 'react'
  import { DefaultGlobalCss } from '../global/GlobalCss'
  import { createTheme, Theme } from './createTheme'
  +import { lightTheme } from './themes'
  export interface ThemeProviderProps {
  theme?: Theme
  children?: React.ReactNode
  }
  -export const ThemeContext = React.createContext<Theme>(null)
  +export const ThemeContext = React.createContext<Theme>(lightTheme)
  export function ThemeProvider(props: ThemeProviderProps) {
  const { theme, children } = props
  