[Console] Handle zero row count in appendRow() for Table

[adam-prickett]

Q	A
Branch?	4.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets	n/a
License	MIT
Doc PR	n/a

When a Table is created and rendered with no rows (headers only) and subsequently rows are added using appendRow(), the first call to appendRow() clears back one line too far., thus removing the last run

This is caused by calculateRowCount() not accounting for the fact that the footer separator is also the header separator when no rows are present.

This PR works around the issue by checking to ensure that at least 1 row exists before including the footer separator in the row count.

Example

Command:

<?php

namespace App\Command;

class TableTestCommand extends Command
{
    // ...

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $output->writeln('My table');

        $table = new Table($output->section());
        $table->setHeaders(['Column', 'Another column']);
        $table->render();
        
        $table->appendRow(['Value', 'Another Value']);
        $table->appendRow(['Value', 'Another Value']);
    }
}

Before fix:

+--------+----------------+
| Column | Another column |
+--------+----------------+
| Value  | Another Value  |
| Value  | Another Value  |
+--------+----------------+

After fix:

My table
+--------+----------------+
| Column | Another column |
+--------+----------------+
| Value  | Another Value  |
| Value  | Another Value  |
+--------+----------------+

[nicolas-grekas]

Thanks for the PR.
Does this issue exist on 3.4?
Please add a test case also.

[adam-prickett]

@nicolas-grekas Furthest back this issue goes is to 4.1. Test case incoming.

[fabpot]

Thank you @adam-prickett.