DRILL-8512: ReduceAndSimplifyFilterRule fails with NullPointerException #4040

Job	Run time
Run checkstyle and generate protobufs	31m 53s
Main Build (8, default-hadoop)	52m 58s
Main Build (11, default-hadoop)	46m 36s
Main Build (17, default-hadoop)	43m 15s
Main Build (8, hadoop-2)	51m 50s
	3h 46m 32s

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