My daughter learned to pull herself up this week. She likes to stand in her crib, but because she just learned she's still very wobbly and falls back. She's hit her head a few times. She doesn't usually wake up in the middle of the night, but this week she has every night. I'm worried she'll wake up and stand in her crib and hit her head while we're sleeping. Any ideas how to prevent or make it safer?

Her crib has nothing in it other than a fitted sheet.