Investigate bug on FF & iPhone with share modal

[rachelfranklin1]

Some firefox users may be experiencing issues with the Share Modal:

Please see conversation here:
https://impact-makers-group.slack.com/archives/CJ42T62DT/p1559746602014600

[mfix22]

This looks like it has already been fixed @rachelfranklin1 🙂 I am not seeing any issues with smooth scrolling on Firefox.