Check if a crater does not generate topography. If not, skip it.

src/crater/crater_populate.f90

@@ -240,6 +240,12 @@ subroutine crater_populate(user,surf,crater,domain,prod,production_list,vdist,nt
 
          ! Place crater onto the surface
          call crater_emplace(user,surf,crater,domain,ejbmass)
+         if (abs(ejbmass) < tiny(ejbmass)) then ! Crater has no topography. Discard and move on.
+            ntrue = ntrue -1
+            mass = mass - crater%impmass
+            cycle
+         end if
+
 
          call ejecta_distance_estimate(user,crater,domain,crater%ejdis) ! Fast but imprecise estimate of the total ejecta distance
                                                                         ! For very steep size distributions, only a fraction of the