Fixed some more phpstan issues

src/Entity/Parts/Part.php

@@ -50,6 +50,8 @@ use Symfony\Component\Validator\Context\ExecutionContextInterface;
  * The class properties are split over various traits in directory PartTraits.
  * Otherwise, this class would be too big, to be maintained.
  * @see \App\Tests\Entity\Parts\PartTest
+ * @extends AttachmentContainingDBElement<PartAttachment>
+ * @template-use ParametersTrait<PartParameter>
  */
 #[UniqueEntity(fields: ['ipn'], message: 'part.ipn.must_be_unique')]
 #[ORM\Entity(repositoryClass: PartRepository::class)]

src/Entity/Parts/PartLot.php

@@ -107,12 +107,12 @@ class PartLot extends AbstractDBElement implements TimeStampableInterface, Named
     protected bool $needs_refill = false;
 
     /**
-     * @var Part The part that is stored in this lot
+     * @var Part|null The part that is stored in this lot
      */
     #[Assert\NotNull]
     #[ORM\ManyToOne(targetEntity: Part::class, inversedBy: 'partLots')]
     #[ORM\JoinColumn(name: 'id_part', nullable: false, onDelete: 'CASCADE')]
-    protected Part $part;
+    protected ?Part $part = null;
 
     /**
      * @var User|null The owner of this part lot
@@ -226,7 +226,7 @@ class PartLot extends AbstractDBElement implements TimeStampableInterface, Named
     /**
      * Return the part that is stored in this part lot.
      */
-    public function getPart(): Part
+    public function getPart(): ?Part
     {
         return $this->part;
     }

src/Entity/Parts/PartTraits/InstockTrait.php

@@ -188,7 +188,7 @@ trait InstockTrait
         $sum = 0;
         foreach ($this->getPartLots() as $lot) {
             //Don't use the in stock value, if it is unknown
-            if ($lot->isInstockUnknown() || $lot->isExpired() ?? false) {
+            if ($lot->isInstockUnknown() || ($lot->isExpired() ?? false)) {
                 continue;
             }