Check for NULL qsort() base pointers

Check for NULL qsort() base pointers

There are a couple of places in wpa_supplicant/hostapd where qsort() can
be called with a NULL base pointer. This results in undefined behavior
according to the C standard and with some standard C libraries (ARM RVCT
2.2) results in a data abort/memory exception. Fix this by skipping such
calls since there is nothing needing to be sorted.

Signed-off-by: Joel Cunningham <joel.cunningham@me.com>