out-of-bounds write nn_bitset_one w multiple of 32

nn_bitset_one sets the specified number of bits by first memset'ing the
words, then clearing bits set in a final partial word.  It mishandled
the case where the number of bits is a multiple of 32, clearing the
entire word following the last one it was to touch.

Signed-off-by: Erik Boasson <eb@ilities.com>

src/core/ddsi/include/dds/ddsi/q_bitset.h

@@ -49,6 +49,7 @@ inline void nn_bitset_one (uint32_t numbits, uint32_t *bits)
   memset (bits, 0xff, 4 * ((numbits + 31) / 32));
 
   /* clear bits "accidentally" set */
+  if ((numbits % 32) != 0)
   {
     const uint32_t k = numbits / 32;
     const uint32_t n = numbits % 32;