Can't tell from the picture, but is the center brace still intact? If it is, you "might" be OK. The center brace is wjat keeps it from bowing at the top. Keep an eye on the gap. If it widens even a bit, that just means it's starting to bow out and you should have "plan B" ready to put into action. Honestly, for long term peace of mind, you should think about either replacing the top brace at the very least. The mfr. usually sells replacements. It's not a small task though.