It seems like there's currently a bug when removing old lines when scrollback is enabled where I can scroll past the oldest line.

I'm guessing in some cases the same bug would also cause not being able to scroll enough to see the oldest line, but I haven't encountered this case yet.

To reproduce: set the scrollback something small. 100 works fine in my case. Then leave the client running for a while in an active channel. Every once in a while try to scroll to the top using page-up/down. You'll end up with a screen like:

---------------
<empty>
<empty>
<empty>
old line
old line
---------------

What should happen instead is I should not be able to scroll after the oldest line is at the top:

---------------
old line
old line
old line
old line
old line
---------------