does anybody know why UPNP GetSecurityKeys option gives me null wpa password?

the WLANConfiguration.xml

the part where GetSecurityKeys is mentioned

<action>
<name>GetSecurityKeys</name>
<argumentList>
<argument>
<name>NewWEPKey0</name>
<direction>out</direction>
<relatedStateVariable>WEPKey</relatedStateVariable>
</argument>
<argument>
<name>NewWEPKey1</name>
<direction>out</direction>
<relatedStateVariable>WEPKey</relatedStateVariable>
</argument>
<argument>
<name>NewWEPKey2</name>
<direction>out</direction>
<relatedStateVariable>WEPKey</relatedStateVariable>
</argument>
<argument>
<name>NewWEPKey3</name>
<direction>out</direction>
<relatedStateVariable>WEPKey</relatedStateVariable>
</argument>
<argument>
<name>NewPreSharedKey</name>
<direction>out</direction>
<relatedStateVariable>PreSharedKey</relatedStateVariable>
</argument>
<argument>
<name>NewKeyPassphrase</name>
<direction>out</direction>
<relatedStateVariable>KeyPassphrase</relatedStateVariable>
</argument>
</argumentList>

i tried googling and the only thing i found was a pdf file called UPnP-gw-WLANConfiguration-v1-Service.pdf the only null word i found in it is this and it have nothing to do with my problem !

i don’t even have that NewPreSharedKeyIndex that is mentioned there in my wlan xml file