we are using Web 8. While publishing items Pages and components are getting published successfully but categories stuck at Committing deployment or waiting for deployment stage.i m getting Object reference not set to an instance of an object error in TcmPublisher.Log
7/21/2016 10:41:45 PM <2060> Receiving deployment feedback for publish transaction [tcm:0-1446981-66560] with status: CommittingDeployment
7/21/2016 10:42:30 PM <2060> Transport service response: <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<TransportSummaries>
<TransportSummary end="2016-07-22T01:42:21.887+03:00" referenceId="tcm:0-1446981-66560" start="2016-07-22T01:41:20.239+03:00" state="Success">
<Processing>
<Context topic="Content Delivery">
<IsRollbackOnFailure>false</IsRollbackOnFailure>
</Context>
<Step end="2016-07-22T01:41:20.250+03:00" href="simple" type="Prepare transport" start="2016-07-22T01:41:20.239+03:00" state="Success">
<RemoteEndpoint connector="DiscoveryService" end="2016-07-22T01:41:20.250+03:00" id="bRdHVRXIfODlWtOgbQ57lQ==" name="Discovery Service Upload" processor="10392@staging-web" start="2016-07-22T01:41:20.239+03:00" state="Success" windowSize="0"/>
</Step>
<Step end="2016-07-22T01:41:20.375+03:00" href="simple" type="Transporting" start="2016-07-22T01:41:20.257+03:00" state="Success">
<RemoteEndpoint connector="DiscoveryService" end="2016-07-22T01:41:20.375+03:00" id="bRdHVRXIfODlWtOgbQ57lQ==" name="Discovery Service Upload" processor="10392@staging-web" start="2016-07-22T01:41:20.257+03:00" state="Success" windowSize="0"/>
</Step>
<Step end="2016-07-22T01:41:33.802+03:00" href="simple" type="Deployment preparation" start="2016-07-22T01:41:33.724+03:00" state="Success">
<RemoteEndpoint connector="DiscoveryService" end="2016-07-22T01:41:33.802+03:00" id="bRdHVRXIfODlWtOgbQ57lQ==" name="Discovery Service Upload" processor="10392@staging-web" start="2016-07-22T01:41:33.724+03:00" state="Success" windowSize="0"/>
</Step>
<Step end="2016-07-22T01:41:39.552+03:00" href="simple" type="Deploying" start="2016-07-22T01:41:33.818+03:00" state="Success">
<RemoteEndpoint connector="DiscoveryService" end="2016-07-22T01:41:39.552+03:00" id="bRdHVRXIfODlWtOgbQ57lQ==" name="Discovery Service Upload" processor="10392@staging-web" start="2016-07-22T01:41:33.818+03:00" state="Success" windowSize="0"/>
</Step>
<Step end="2016-07-22T01:42:21.887+03:00" href="simple" type="Deployment committing" start="2016-07-22T01:42:21.575+03:00" state="Success">
<RemoteEndpoint connector="DiscoveryService" end="2016-07-22T01:42:21.887+03:00" id="bRdHVRXIfODlWtOgbQ57lQ==" name="Discovery Service Upload" processor="10392@staging-web" start="2016-07-22T01:42:21.575+03:00" state="Success" windowSize="0"/>
</Step>
</Processing>
</TransportSummary>
</TransportSummaries>
7/21/2016 10:42:30 PM <2060> Receiving deployment feedback for publish transaction [tcm:0-1446981-66560] with status: Success
7/21/2016 10:42:30 PM <2060> Object reference not set to an instance of an object.