Adding extra spaces inside list blocks results in various crashes. I also observed similar issues when working on adding multiline image captions.

Test Scenarios

1. (1) Begin editing new list, (2) add two spaces, (3) add any letter, (3) press Enter, and 💥
2. (1) Begin editing new list, (2) add three spaces, (3) press Enter, and 💥
3. (1) Begin editing new list, (2) add any letter, (3) add three spaces (second space creates a period), (4) press Enter, and 💥

All of these crashes are pretty similar, so just including a gif of the first scenario (space-space-letter) as an example: