Redraw interface after launching external viewer

[n-st]

GUI programs tend to output warnings on their stdout or stderr.
In paperboy, those warnings overwrite part of the user interface:

It should be sufficient to redraw the interface when the external viewer terminates, as paperboy is unresponsive while waiting for the external program anyway.

[2mol]

Thanks for raising this! I will try to reproduce this and see if I can figure out how to suppress the output of the child program, or redraw when necessary.