on small screen menu may fall off top of screen

Created by: jhnc

[Duplicate of https://github.com/misd-service-development/drupal-cambridge-theme/issues/31 which I was told should be here.]

Using the small screen display, with a menu like:

• 1
• 2
  • 2a
  • 2b
  • 2c
  • 2d
  • 2e
  • 2f
  • 2g
  • 2h
  • 2j
  • 2k
  • 2l
  • 2m
  • 2n
  • 2o
  • 2p
  • 2q
  • 2r
  • 2s
    • 2sA
    • 2sB

if one has to scroll down a long way to reach 2s, then when one selects it, 2sA/2sB will be off the top of the screen.