MFH: r440736

games/acm: prevent free()ing unitialized data

acm may coredump immediately after starting on systems which do not
zero malloc()ed memory e.g., MALLOC_CONF=junk:true. This is because
one of the fields of a malloc()ed data structure (w) contains a
pointer (w->csPool2), and if that pointer is never used, then later
code will find the pointer is non-NULL and try to free() the memory
pointed to by the pointer.

PR: 215427
Submitted by: Jeff Gibbons <jgibbons@protogate.com>
Approved by: ports-secteam blanket