My gutter is leaking at the corner. After some youtubing, it seems like I'd want to just re-seal the miter (essentially just caulk). However, mine seems to have a rubber-like substance along the whole bottom of the inside of the gutter (the red arrow in the picture points to the edge of the peeling material). I didn't see this in any of the gutter installation videos I watched - what is it called? Can I just pull this up (it's really stuck on there) so I can re-caulk the seam?