Fix bottom scrolling bug.
Fix bottom scrolling bug.

This fixes the bug where new messages would not be scrolled-to. Instead,
the last-but-one message was scrolled to.

sirodoht/ting,gtklocker/ting,dionyziz/ting,VitSalis/ting,mbalamat/ting,odyvarv/ting-1,gtklocker/ting,gtklocker/ting,VitSalis/ting,dionyziz/ting,dionyziz/ting,mbalamat/ting,sirodoht/ting,gtklocker/ting,sirodoht/ting,odyvarv/ting-1,odyvarv/ting-1,VitSalis/ting,odyvarv/ting-1,VitSalis/ting,sirodoht/ting,mbalamat/ting,dionyziz/ting,mbalamat/ting