spark git commit: [SPARK-15814][SQL] Aggregator can return null result

Repository: spark Updated Branches: refs/heads/branch-2.0 41f309bfb -> d64cb1994 [SPARK-15814][SQL] Aggregator can return null result ## What changes were proposed in this pull request? It's similar to the bug fixed in https://github.com/apache/spark/pull/13425, we should consider null objec

spark git commit: [SPARK-15814][SQL] Aggregator can return null result

Repository: spark Updated Branches: refs/heads/master d681742b2 -> cd47e2337 [SPARK-15814][SQL] Aggregator can return null result ## What changes were proposed in this pull request? It's similar to the bug fixed in https://github.com/apache/spark/pull/13425, we should consider null object an