Make return value nullable

[bencroker]

This PR fixes a bug in which a type error which is thrown if a multi select condition rule is added without any values, as reported in putyourlightson/craft-campaign#367. This is caused by OptionsFieldConditionRule::elementQueryParam having a strict return type of array, whereas the paramValue method has a nullable return type of ?array.

cms/src/fields/conditions/OptionsFieldConditionRule.php

Lines 38 to 41 in 3a5ca05

	protected function elementQueryParam(): array
	{
	return $this->paramValue();
	}

The error encountered is as follows.

2023-02-21 06:56:47 [web.ERROR] [TypeError] craft\fields\conditions\OptionsFieldConditionRule::elementQueryParam(): Return value must be of type array, null returned {"trace":["#0 /home/www/manufacture.scandella.fr/htdocs/vendor/craftcms/cms/src/fields/conditions/FieldConditionRuleTrait.php(115): craft\\fields\\conditions\\OptionsFieldConditionRule->elementQueryParam()","#1 /home/www/manufacture.scandella.fr/htdocs/vendor/craftcms/cms/src/elements/conditions/ElementCondition.php(181): craft\\fields\\conditions\\OptionsFieldConditionRule->modifyQuery()","#2 /home/www/manufacture.scandella.fr/htdocs/vendor/putyourlightson/craft-campaign/src/services/SegmentsService.php(142): craft\\elements\\conditions\\ElementCondition->modifyQuery()"

[brandonkelly]

Thank you!

[brandonkelly]

4.3.11 is out with that fix.