[lldb] Statusline resizing quirk

In #202691, @labath reported an issue when resizing the statusline:

> I noticed one additional quirk when playing around with this. If I increase the window height abruptly (say, using the "maximize vertically") feature, then we end up with a bunch of blank lines between the prompt (which is at the bottom of the screen) and whatever was on the screen before the resize. If I resize the window slowly (so ~one line at a time), Then the blank lines don't show up, and the window fills with the lines that were previously not visible.
>
> Interestingly, this happens only once -- if I resize the window back-and-forth multiple times, we don't keep inserting new blank lines.