patch 9.1.1476: missing out-of-memory checks in cmdexpand.c

patch 9.1.1476: missing out-of-memory checks in cmdexpand.c

Problem:  missing out-of-memory checks in cmdexpand.c
Solution: add missing out-of-memory checks, re-order code
          (John Marriott)

This commit does the following:
- in cmdline_pum_create() add out-of-memory check call of ALLOC_MULT()
- in expand_cmdline() move check for out-of-memory to cover both
  assignments of file_str
- in nextwild() don't free `p2` until after it's last use.

closes: #17592

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