Fixed missing values on transposing.

[doekenorg]

Requirements for this bug:

• No multiple rows enabled
• Checkbox field without values in the entry
• Transposing the export

If a checkbox list had no selected values in the entry it would not yield any result, making the resulting entry row incomplete compared to the fields list. This is no problem for a normal export, but when transposing the array mismatch creates a broken array.

example:

$output = [
    //fields
    [
        0 => 'Some field',
        1 => 'checkbox list field',
        2 => 'third field',
    ],
    // results
    [
        0 => 'Some value',
        2 => 'third value',
    ]
];

// Broken:
$transposed = [
    [ 'Some field', 'some value' ],
    [ 'checkbox list field', 'third value' ],
    [ 'third field' ]
];