Refactored code:

```bash
function addModelToIndexFile {
    responseWords=$(wc -w < "$modelFile" | awk '{print $1}')
    responseBytes=$(wc -c < "$modelFile" | awk '{print $1}')

    (
        echo "<tr><td class='left'><a href='./$model.html'>$model</a></td><td>$responseWords</td><td>$responseBytes</td>"
        while read -r line; do
            value=$(echo "$line" | cut -d ':' -f2)
            if [[ -n "$value" ]]; then
                echo "<td>$value</td>"
            fi
        done < "$statsFile"
        echo "</tr>"
    ) >> "$indexFile"
}
```

This code removes the need for a temporary array, directly reading from `$statsFile` and outputting to the index file. It also eliminates the need for looping through an array.