Fixes an issue where pan & pinch on iPad do not work on the region where the minimap would be shown when the minimap is hidden. Does this by extracting and using a new fn should_show_mini_map.

QA:

• pan using the minimap
• pan canvas in the minimap area when it's off
• pan canvas in the minimap area when not in notebook mode
• pan canvas in the minimap area when overlay is hidden

side note: it's sensible to only show the minimap in scroll mode but confusing that you can have show minimap on and not see the minimap