warning: Deprecated function: str_replace(): Passing null to parameter #3

From the logs,

Deprecated function: str_replace(): Passing null to parameter #3 (closed) ($subject) of type array|string is deprecated in Drupal\filter\Element\ProcessedText::preRenderText() (line 101 of /opt/drupal/web/core/modules/filter/src/Element/ProcessedText.php)

After a quick investigation, I believe the root of the issue is here: https://gitlab.eclipse.org/eclipsefdn/it/websites/drupal/eclipsefdn/-/blob/9.1.x/eclipsefdn_projects/src/Entity/ProjectNode.php?ref_type=heads#L930

We are passing values that are expected to be string but they are NULL in some situations.