In dda14abb3c51166553015ef489e9ac9acb859904, GPGCleanup added 'set
buffhidden=hide' to try avoiding error messages when modified buffers
are being abandoned. However, that only works if the buffer is the last
visible buffer.
If there are windows displaying multiple buffers, then errors can still
be emitted. Using "only!" ensures all the other windows can be closed.
Signed-off-by: James McCoy <jamessan@jamessan.com>
45fdaf52ed