Weights in new crime procedures fail sometimes

[mariopaolucci]

Run #15, RUNTIME ERROR: Extension exception: Got -0.02934005120594313 as a wei
ght but all weights must be >= 0.0.
error while observer running RND:WEIGHTED-ONE-OF
  called by (anonymous command: [ cell -> let last table:get c-range-by-age-an
d-sex cell let persons with [ age > last cell and age <= first value and male?
 = first cell ] let last value * count people-in-cell / ticks-per-year * crime
-multiplier repeat round target-n-of-crimes [ set number-crimes number-crimes 
+ 1 ask rnd:weighted-one-of people-in-cell [ criminal-tendency + criminal-tend
ency-addme-for-weighted-extraction ] [ let find-accomplices number-of-accompli
ces set co-offender-groups lput accomplices co-offender-groups if oc-member? [
 set co-offenders-started-by-OC lput accomplices co-offenders-started-by-OC ] 
if count accomplices > this-is-a-big-crime and criminal-tendency < good-guy-th
reshold [ set big-crime-from-small-fish big-crime-from-small-fish + 1 ] ] ] ])
  called by procedure COMMIT-CRIMES