Fix query builder constraints

[Umair-exe]

Description

Visual changes

Functional changes

• Code style has been fixed by running the composer cs command.
• Changes have been tested to not break existing functionality.
• Documentation is up-to-date.

[People-Sea]

LGTM. This defensive fix addresses the issue.

The root cause is a state/schema cache synchronization issue, but this null check is a reasonable and low-risk solution.

[danharrin]

I would like to understand the cause of the error before choosing to silence it like this, I'm confused why the synchronisation issue is there based on the issue description

[People-Sea]

I would like to understand the cause of the error before choosing to silence it like this, I'm confused why the synchronisation issue is there based on the issue description

@danharrin From my debugging, it seems related to statePath switching in applyFiltersToTableQuery() causing cachedDefaultChildSchemas to be built from the wrong statePath.

[Umair-exe]

When getChildSchema($ruleIndex) is called with a non-default key (the rule index), and if there are no components registered for that key, the method returns null instead of returning an empty schema.

This happens in the Builder component when iterating through rules. The $ruleBuilder->getChildSchema($ruleIndex) call expects to get a child schema for each item/rule, but when the $ruleIndex doesn't have cached child schemas yet, it returns null.

[danharrin]

I think #19128 addresses the root issue instead of silencing it

I would appreciate @Umair-exe to check if it still solves their problem and @People-Sea to review if the code is sane or not - thanks for your comment about the child schema caching, that made it easy to trace the problem