Turns out there are some cases where the Cray
wlm_detect_get_active may return NULL, in which
case fallback to wlm_detect_get_default method
is suggested. Make use of the fallback to
avoid segfaults under some circumstances in the
ALPS plm selection method.
Signed-off-by: Howard Pritchard <howardp@lanl.gov>
69200e6229