Fix previous change to (next|previous)-buffer

* lisp/window.el (next-buffer, previous-buffer): If no other
buffer is available, signal 'user-error' only when called
interactively.
1 job for master in 67 minutes and 36 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #4356
test-all

01:07:36

 
Name Stage Failure
failed
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 2
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1