Getting error while deleting entities in Project server 2013 using asmx web service through Soap UI

Question

I want to remove task from project in project server 2013 using Soap UI via its exposed asmx services, but i am getting ProjectServerError(s) LastError=GeneralUnhandledException while doing operation through Soap UI and java code also.

My request body is :

  <proj:QueueDeleteFromProject>
     <proj:jobUid>4b86f225-cbe8-e411-a291-005056ad0474</proj:jobUid>
     <proj:sessionUid>4b86f225-cbe8-e411-a291-005056ad0473</proj:sessionUid>
     <proj:projectUid>4b86f225-cbe8-e411-a291-005056ad0472</proj:projectUid>
     <proj:projectEntityUids>
       <proj:guid>ee6566d1-cbe8-e411-a291-005056ad0472</guid>
       <proj:guid>84d6b846-f4e8-e411-a291-005056ad0472</guid>
     </proj:projectEntityUids>
  </proj:QueueDeleteFromProject>

And the response is :

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
   <s:Body>
      <s:Fault>
         <faultcode>s:Server</faultcode>
         <faultstring xml:lang="en-US">ProjectServerError(s) LastError=GeneralUnhandledException Instructions: Pass this into PSClientError constructor to access all error information</faultstring>
         <detail>
            <errinfo>
               <general>
                  <class name="General Unhandled Exception in _Project.QueueDeleteFromProject_">
                     <error id="42" name="GeneralUnhandledException" uid="ce084759-96f8-e411-97e7-005056ad0472" Exception="System.Data.SqlTypes.SqlNullValueException: Data is Null. This method or property cannot be called on Null values.
   at System.Data.SqlClient.SqlBuffer.get_String()
   at Microsoft.Office.Project.Server.DataAccessLayer.ProjectDal.GetSessionInfo(Guid projectUid, Guid&amp; sessionID, String&amp; sessionDescription)
   at Microsoft.Office.Project.Server.BusinessLayer.Project.ValidateSession(Guid projectUid, Guid sessionUid)
   at Microsoft.Office.Project.Server.BusinessLayer.Project.QueueDeleteFromProject(Guid jobUid, Guid sessionUid, Guid projectUid, Guid[] projectEntityUids)
   at Microsoft.Office.Project.Server.Wcf.Implementation.ProjectImpl.&lt;>c__DisplayClass75.&lt;QueueDeleteFromProject>b__74()
   at Microsoft.Office.Project.Server.Wcf.Implementation.WcfMethodInvocation.InvokeBusinessObjectMethod(String businessObjectName, String methodName, IEnumerable`1 actions)"/>
                  </class>
               </general>
            </errinfo>
         </detail>
      </s:Fault>
   </s:Body>
</s:Envelope>

Please help me with this issue. Thanks in advance. Also mention any suggestions if you have.