FD3-445 set null en cablemodem al borrar cablemodemModel

src/CablemodemBundle/Entity/Cablemodem.php

@@ -96,6 +96,7 @@ class Cablemodem implements DeviceInterface, TenancyIdTraitInterface, LocationIn
 
     /**
      * @ORM\ManyToOne(targetEntity="CablemodemModel", fetch="EXTRA_LAZY")
+     * @ORM\JoinColumn(onDelete="SET NULL")
      * 
      * @JMS\MaxDepth(1)
      */