Mercure Publish fails if expression returns bool false

[dennobaby]

API Platform version(s) affected: 2.5

Description
Mercure Publish fails if an expression is used which could return false:
The value of the "mercure" attribute of the "MyClass" resource class must be a boolean, an array of options or an expression returning this array, "boolean" given.'

How to reproduce

/**
  * @ApiResource(
  *    mercure="object.mercure()"
  * )
  */
class MyClass
{
[...]
    private function mercure(){
        return false;
    }
}

Possible Solution
Maybe just move the if-clause in

core/src/Bridge/Doctrine/EventListener/PublishMercureUpdatesListener.php

Line 157 in 38d69e6

if (false === $options) {

after the expression-evaluation in

core/src/Bridge/Doctrine/EventListener/PublishMercureUpdatesListener.php

Line 161 in 38d69e6

if (\is_string($options)) {

[stephanvierkant]

I'm having the same problem. I'll try to create a PR.