patch 9.1.1270: missing out-of-memory checks in buffer.c

patch 9.1.1270: missing out-of-memory checks in buffer.c

Problem:  missing out-of-memory checks in buffer.c
Solution: handle out-of-memory situations during allocation
          (John Marriott)

closes: #17031

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>