Im afraid once these come apart like it has you cannot fix it back. Ive seen it before were people have tried super glue and high temperature sealent and it still come apart. They are factory bonded so once it comes off like this you just need to replace the seal.
Click here for the part
They are very easy to replace as they are just clipped into each corner so unclip the corner and then you can remove the seal and fit a new one.
Ive seen it loads of times on there and it always ends up with a new seal.
If you need anymore info just get back to me.