simulink function variable output problem

I have a function that lets say can have an output of variable size array between 1 and 10 elements I have set y as variable size as [1,10] in the Edit Data window The code in if 0 ... works correctly and return variable size arrays of size 9 or 10 When I try to run code above if 0 i get (initially was commented)

Size mismatch (size [0 x 0] ~= size [1 x 2]).
The size to the left is the size of the left-hand side of the assignment.

Function 'FrameGenerator/AddEscapeCharacter1/MATLAB Function' (#23.281.291), line 9, column 3:
"finalArray"

How to fix this lol ?

Here is the code

function y = addEscapeCharacter(frameBytes, escapeCharacter, startOfFrame) %codegen
finalArray =  single([]);

%coder.varsize('y',[1,10]);

for i =1:length(frameBytes)
  currentFrameByte = frameBytes(i);
  if currentFrameByte == escapeCharacter || currentFrameByte == startOfFrame
    finalArray = horzcat([escapeCharacter,frameBytes(i)], finalArray);
  else
    finalArray = horzcat([currentFrameByte], finalArray);
  end
end

if 0
  if randi(2) ==1
    finalArray = horzcat(single( [1 2 3 4 5 6 7 8 9]) , single([6]));
  else
    finalArray = horzcat(single( [1 2 3 4 5 6 7]),  single([6]), single([1]));
  end
end
%print('%d', length(finalArray));

y = single(finalArray);

Answer 1

[timo]

Ok i solved it with this modifications

function y = addEscapeCharacter(frameBytes, escapeCharacter, startOfFrame) %codegen
finalArray =  single([]);

coder.varsize('finalArray',[1, 2 * length(frameBytes)]);

for i =1:length(frameBytes)
  currentFrameByte = frameBytes(i);
  if currentFrameByte == escapeCharacter || currentFrameByte == startOfFrame
    finalArray = horzcat(finalArray,[escapeCharacter, currentFrameByte]);
  else
    finalArray = horzcat(finalArray,[currentFrameByte]);
  end
end

y = single(finalArray);

I hope is the most efficient way This function adds to a frame escape characters for ESC char and start of frame as described in the Link Layer OSI Framing protocol