How can I solve this error "Improper assignment with rectangular empty matrix." when I run the listed below script.. thanks in advance

elevtocellsI1=accumarray(OrbNO,elev2,[],@(x) {x});
DDDD=zeros(1,size(elevtocellsI1,1));
for i=1:size(elevtocellsI1,1)
DDDD(i)=(find(elevtocellsI1{i}, 1, 'last' )-(find(elevtocellsI1{i}, 1 )))/60;
end

[Walter Roberson]

Duplicated by later http://www.mathworks.com/matlabcentral/answers/319713-how-can-i-solve-this-error-improper-assignment-with-rectangular-empty-matrix-with-listed-below-sc which has an answer