Error with mex file ... ....Index exceeds matrix dimensions. Index value 3 exceeds valid range [1-2] of array gesgroup.

I have a function file to mex file. But it is giving error when running the mex file. Following is the code.

In the code I have initialised 3 vectors named group,horgroup,gesgroup and declared gesgroup as varsize.

group = zeros(1,2);    
horgroup = zeros(1,2); 
gesgroup = zeros(1,2); 
coder.varsize('gesgroup');

in few lines group and horgroup are calculated as arrays of size (1 * 2) say group = [1 2] and horgroup = [3 4] later i need to merge group and horgroup into gesgroup using

gesgroup = [group, horgroup];
gesgroup(gesgroup==0) = NaN;

this code is not giving any error while generating a mex file but when I am running the mex file its giving error in above two lines, saying "Index exceeds matrix dimensions. Index value 3 exceeds valid range [1-2] of array gesgroup"

Let me know if I need to change anything in the code and generate the mex file again.