Modal gatsby patch

[ZeMunchkin]

In this PR

• move reference to document inside of component to fix gatsby build error

Problem:
Getting build error on Gatsby b/c document is not defined at build-time on Heroku.

Gatsby docs on issue -- they suggest moving the reference to document to a place that won't be called until document is defined:
https://www.gatsbyjs.org/docs/debugging-html-builds/

To fix this, moved the reference to the document inside the component so that document is defined by the time the reference is made.