<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
                    http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">

 <mapped-superclass name="PlFort\CasAuthBundle\Entity\CasServer">

        <field name="httpProtocol" column="http_protocol" type="string" length="5" />

        <field name="host" column="host" type="string" length="255"/>

        <field name="port" column="port" type="integer" />

        <field name="protocolVersion" column="cas_version" type="integer" />

        <field name="caCertFile" column="ca_certificate" type="string" length="500"/>
   </mapped-superclass>
</doctrine-mapping>
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
                    http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">

 <mapped-superclass name="PlFort\CasAuthBundle\Entity\CasServer">

        <field name="httpProtocol" column="http_protocol" type="string" length="5" />

        <field name="host" column="host" type="string" length="255"/>

        <field name="port" column="port" type="integer" />

        <field name="protocolVersion" column="cas_version" type="integer" />

        <field name="caCertFile" column="ca_certificate" type="string" length="500" nullable="true"/>
   </mapped-superclass>
</doctrine-mapping>
Allow null in caCertFile column
Allow null in caCertFile column