update Gridded_to_Mesh_SeaBed_DepthAveraged.m to fix the infinite loop in using Cal_IT_Fric.m

[Jiangchao3]

The IT calculation process sometimes gets stuck in an infinite loop when using the original N data. Here NaNs in the originally generated N data in the vertical direction are firstly filled by extrapolating all N values down the column using the nearest non-NaN value above.

[WPringle]

I'm wondering about these lines:

 [~,index_lon_min] = min(abs(lon_N-min(lon_M)));
 [~,index_lon_max] = min(abs(lon_N-max(lon_M)));
 [~,index_lat_min] = min(abs(lat_N-min(lat_M)));
 [~,index_lat_max] = min(abs(lat_N-max(lat_M)));

With the use of the abs() of the difference then the difference could be negative and therefore would not encompass the full extents of lat_M, lon_M.
For example, for
[~,index_lat_max] = min(abs(lat_N-max(lat_M)));
if lat_N = [4.5, 4.9, 5.2], and max(lat_M) = 5 then the smallest absolute difference is for lat_N = 4.9, but that is less than max(lat_M) = 5.
So as a post-processing we would want to add 1 to index_lat_max to have that at the 5.2 value, right? I think need to test that if lat_N(index_lat_max) < max(lat_M) then add 1 (assuming that index_lat_max < length(lat_N)).
Similar post-processing should be done for all four indices.

[Jiangchao3]

Hi @WPringle, agree with you and I add four if-end conditions to address the boundary values. Please review. Thanks.

[WPringle]

Looks good thank you!

[krober10nd]

Change log and link PR.