FPII-2676:Ensure that NLSF cannot be negative when computing a min distance between them

b/31607432

Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>
(cherry picked from commit d9d5ac4027c5ee1da2ff1c6572ae3b35a845db19)

Change-Id: I9f979da17f0879d2f4f06ae9325e5fde54ce27ef
1 file changed