Canvas doesn't draw rectangle after for loop

I'm trying to create a news ticker that renders text in small square "pixels". I say "pixels" because they look like pixels, but the actual displayed square is larger than 1px.

So far I can get all the rendered letters from the object I build (containing the pixel coordinates of each rectangle). The code can be viewed here : https://jsfiddle.net/9u3ez6gu/2/

The letters are rendered correctly, but after the for loop (see code sample below) I am trying to create a lime white space between each letter. No matter what I do, this lime space never gets rendered. Here is the for loop and the code I am using to render the space. Does anyone know why canvas won't let me draw lime rectangles?

for (i = 0; i <= inv[letter].length; i++) {
    var x = inv[letter][i][1] * full;
    var y = inv[letter][i][0] * full;
    context.beginPath();
    context.rect(x, y, unit, unit);
    context.fillStyle = 'black';
    context.closePath();
    context.fill();
}// End for loop

//Add a gap between letters
var gapx = full * 5;
context.beginPath();
context.rect(gapx, 0, full, full);
context.fillStyle = 'lime';
context.closePath();
context.fill();
}// End function