I don't know that eggplant, but I have eggplants in the garden and they can take a light freeze. I don't think 50 is low enough to cause any damage to yours, even in a pot. Actually, 2 of mine are in large containers and they made it through last winter just fine, with a couple of light freezes.

You know eggplants aren't annuals? They are perennials and are vegetables. You might get better response if you ask this on the vegetable forum. I've had them live 4 years, until a really hard freeze killed them.

Wonder Eggplant is also known as ornamental eggplant or easter eggplant. So, it's not a real eggplant. The fruit isn't edible.

You can count on it being taken out in the first frost or freeze. I would empty the container, and store it away for next year's plant. I take it that you enjoyed your Easter egg plant? I've never grown one but they look interesting.