Empty string '' as first option triggers Badly-formatted @param in docblock

[jsiefer]

See https://psalm.dev/r/1fe571f7b8

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/1fe571f7b8

<?php

/**
 * @param ''|'a'|'b' $v
 */
function testBad(string $v): void {
    echo $v;
}

/**
 * @param 'a'|'b'|'' $v
 */
function testGood(string $v): void {
    echo $v;
}

Psalm output (using commit 5c784dc):

ERROR: InvalidDocblock - 6:1 - Badly-formatted @param in docblock for testBad