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Hi,

especially after displaying the agenda when it didn't exist before, when
I display it (`org-agenda'), switch to it and then move point to the end
of the agenda buffer, and hit f (`org-agenda-later'), I see an purely
void window.  I don't think I messed with agenda displaying, so others
may be able to reproduce this issue.

Hitting C-g suddenly shows everything as expected - do I just need a
redisplay?  Yip, this fixes the issue for me: