empty() check ignored after fgetcsv()

[thbley]

psalm 3.12.3 gives: Argument 1 of strval cannot be null, possibly null value provided
psalm 3.12.2 gives: no error

https://psalm.dev/r/eb1c5f9e86

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/eb1c5f9e86

<?php
$headers = fgetcsv(fopen('test.txt', 'r'));
if (empty($headers)) {
    throw new Exception('invalid headers');
}
print_r(array_map('strval', $headers));

Psalm output (using commit 5635070):

ERROR: PossiblyNullArgument - 6:29 - Argument 1 of strval cannot be null, possibly null value provided

[muglug]

technically fgetcsv can return [null] which passes the empty check, but in reality that's incredibly rare.