Defensive coding

modules/salesforce_mapping/src/Plugin/Validation/Constraint/UniqueFieldsConstraintValidator.php

@@ -34,20 +34,27 @@ class UniqueFieldsConstraintValidator extends ConstraintValidator {
       $value = $entity->{$field_name}->{$property};
       $query->condition($field, $value);
     }
-
-    if ($id = $query->execute()) {
-      $id = reset($id);
-      $entity = \Drupal::entityTypeManager()
-        ->getStorage($entity_type->id())
-        ->load($id);
-      $url = $entity->toUrl();
-      $message_replacements = [
-        '@entity_type' => $entity_type->getSingularLabel(),
-        ':url' => $url->toString(),
-        '@label' => $entity->label(),
-      ];
-      $this->context->addViolation($constraint->message, $message_replacements);
+    $id = $query->execute();
+    if (empty($id)) {
+      return;
+    }
+    $id = reset($id);
+    if (empty($id)) {
+      return;
+    }
+    $entity = \Drupal::entityTypeManager()
+      ->getStorage($entity_type->id())
+      ->load($id);
+    if (empty($entity)) {
+      return;
     }
+    $url = $entity->toUrl();
+    $message_replacements = [
+      '@entity_type' => $entity_type->getSingularLabel(),
+      ':url' => $url->toString(),
+      '@label' => $entity->label(),
+    ];
+    $this->context->addViolation($constraint->message, $message_replacements);
   }
 
 }