Merge pull request #18070 from craftcms/bugfix/propagate-required-and-field

don't assume we have a field

Author: brandonkelly

src/elements/NestedElementManager.php

@@ -858,7 +858,7 @@ private function saveNestedElements(ElementInterface $owner): void
                     $this->propagationMethod !== PropagationMethod::All &&
                     ($owner->propagateAll || !empty($owner->newSiteIds))
                 ) ||
-                ($owner->propagateRequired && $this->field->layoutElement->required)
+                ($owner->propagateRequired && $this->field?->layoutElement->required)
             ) {
                 // Find the owner's site IDs that *aren't* supported by this site's nested elements
                 $ownerSiteIds = array_map(
@@ -925,7 +925,7 @@ private function saveNestedElements(ElementInterface $owner): void
                             // its elements have been replaced by the other sites’ nested elements
                             if ($owner->propagateAll) {
                                 $this->duplicateNestedElements($owner, $localizedOwner, force: true);
-                            } elseif ($owner->propagateRequired && $this->field->layoutElement->required) {
+                            } elseif ($owner->propagateRequired && $this->field?->layoutElement->required) {
                                 // if we're propagating required and the field is required, and it doesn't validate because of this field,
                                 // duplicate like above
                                 $localizedOwner->setScenario(Element::SCENARIO_LIVE);