Point tree height information convert to raster

SaraQuin

Hello,

I´m working with tree height information. My original file has some blanck parts in the middle because in this part of the site we don´t have vegetation.

When I try to convert this information in a raster file, in the middle of these blank appear some height information (images attached).

I use the manu Analysis-- create elevation grid 

Can you help me to solve this issue? I would like to have a map with this gaps in the vegetation. At least having the 0 value in this part of the map.

Many thanks