SharedUser parameter declaration

I am using K2 smartform in workflow task, it is working fine when normal task assigned to user. 

But when i set Out of office then task url generate with SharedUser paramater and that causing an issue to open smartform.

I created parameter at form level "ShareUser" but when i create task url generate as below:-

https://ABC.onk2.com/Runtime/Runtime/Form/FormName/?SerialNo=111351_61&SharedUser=&SharedUser=AAD:*personal details removed*

Can any one tell me how to pass SharedUser paramter value on form.