lib/inflate.c: handle failed malloc()

lib/inflate.c (inflate_dynamic): Don't deref NULL upon failed malloc.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>