Graphics: Fix a NULL issue in PVRSRVInsertCommandKM

Graphics: Fix a NULL issue in PVRSRVInsertCommandKM

BZ: 35113

In the normal path, the psSwapChain->ppsLastSyncInfos[j] would not
be NULL. But in some error exit path, for example, PVRSRVGetQueueSpaceKM
failed, the psSwapChain->ppsLastSyncInfos[j] may be NULL.

Need to filter out the NULL in psSwapChain->ppsLastSyncInfos.

Change-Id: Ieba6c3659c77f3341f8ddf8003a0f10a13b772fd
Signed-off-by: gwang23 <gang.a.wang@intel.com>
Reviewed-on: http://android.intel.com:8080/49132
Reviewed-by: Tu, Yun <yun.tu@intel.com>
Reviewed-by: Xu, Randy <randy.xu@intel.com>
Reviewed-by: Hu, Austin <austin.hu@intel.com>
Tested-by: Tong, BoX <box.tong@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>