Check for null mBlastBufferQueue

If there is a sync transaction, but blast is not enabled,
mNextDrawUseBLASTSyncTransaction will be true, but mBlastBufferQueue
will be null. This will cause a NPE when trying to call
mBlastBufferQueue.setNextTransaction

Test: Use sync transaction without blast
Fixes: 154527936
Change-Id: Ibff2de7fc7460f882acaceb0182c68ea4b05afb7
1 file changed