Sorry for the bad news, but hopefully Apple will approve the fix quickly.
If you attempt to rate a food already added to your meal (by tap-and-hold-ing on a food in the upper green portion of the meal detail screen) when NO meals are listed below (in the white portion, for example if a search or sort/filter means no other foods are shown), the app will crash.
The work-around is simple:
Just make sure to clear out any search, or change any sort, such that meals are shown in the lower (white) section before rating foods that are already part of the meal you are modifying.
Again, sorry for the issue. The fix is submitted and should be coming soon! (hopefully in 1-2 weeks)