Currently showModalBottomSheet() allows dismissing the displayed sheet by tapping on its body.
The modal bottom sheet should not dismiss upon tapping the general body.

See https://material.io/design/components/sheets-bottom.html#modal-bottom-sheet, modal bottom sheets can only be dismissed by:

• Tapping a menu item or action within the bottom sheet
• Tapping the scrim
• Swiping the sheet down
• Using a close affordance within the bottom sheet’s top app bar, if available

I can work around this with an opaque noop gesture detector around the sheet widget, but the default behavior ought to conform to material spec.