Handle localstorage 'access denied exception'

[schutm]

Using my, webkit based, Vivaldi browser I noticed accessing window.localStorage doesn't return undefined, but throws an access denied exception. Therefor I wrapped the wnidows##localStorage calls in a try... with block.

[joprice]

This might be easier to merge if you make use of the existing npm lock file so that the bucklescript version isn't changed, resulting in such a significant diff, and removing the yarn lock file, since this project doesn't seem to use yarn.