Error in port widths or dimensions.

Greetings to all I have the following error.

Error in port widths or dimensions. Invalid dimension has been specified for input port 1 of 'simulacao_julio6/Integrator1'.

this is my code

function dot_theta = Richards(theta,K,D,thetaz_0,thetaz_f)

L=1; %comprimento

z=linspace(0,L,100); % espaco de discretizacao

dz=L/length(z);

b=1/(2*dz^2);

i=max([1 0 2])+1:length(z),

dot_theta=(1/(2*dz))*((D(i+1)+D(i)).*(theta(i+1)-theta(i))/dz -(D(i-1)+D(i)).*(theta(i)-theta(i-1))/dz+(K(i)-K(i-1)));

%condicao de contorno1

%Se o indice do primeiro elemento do vetor for 1 em vez de 0, seria:

dot_theta(1)=dot_theta(1)+thetaz_0/dz;

%Condicao de contorno no ultimo elemento:

dot_theta(99)=dot_theta(99)-thetaz_f/dz;

my blocks