Always set InputTransparent before _mainViewGrid.Opacity

There is definitely a bug in the order you set these.

CORRECT way to avoid bug:

_mainViewGrid.InputTransparent = section != ComposeSection.None;
_mainViewGrid.Opacity = section == ComposeSection.None ? 1 : 0;

Incorrect way which results in invisible tap regions:

_mainViewGrid.Opacity = section == ComposeSection.None ? 1 : 0;
_mainViewGrid.InputTransparent = section != ComposeSection.None;