@property-read dynamic property type not working sometimes

[M393]

https://psalm.dev/r/f818e2d9d9

Type of $_c should be string instead of ''|mixed.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/f818e2d9d9

<?php

/**
 * @property-read string|null $p
 */
class CCC {
    public function __get(string $name) {
        return null;
    }
    public function f(): void {
        $_c = $this->p ?? '';
		/** @psalm-trace $_c */
    }
    public function g(): void {
        $_a = $this->p;
        $_b = $this->p ?? '';
		/** @psalm-trace $_a $_b */
    }
}

$_d = (new CCC())->p;
/** @psalm-trace $_d */

Psalm output (using commit 03ee02c):

INFO: Trace - 22:24 - $_d: null|string

INFO: Trace - 12:0 - $_c: ''|mixed

INFO: Trace - 17:0 - $_a: null|string

INFO: Trace - 17:0 - $_b: string