GroupByContainerCount.balance() should guard against null LocalityManager

org.apache.samza.SamzaException: Failed to run application
	at org.apache.samza.runtime.LocalApplicationRunner.run(LocalApplicationRunner.java:136)
	at com.linkedin.beam.runners.samza.runtime.fluent.FluentRuntime$RunnerTask.run(FluentRuntime.java:114)
	... 1 more
Caused by: java.lang.NullPointerException
	at org.apache.samza.container.grouper.task.GroupByContainerCount.balance(GroupByContainerCount.java:92)
	at org.apache.samza.coordinator.JobModelManager$.readJobModel(JobModelManager.scala:257)
	at org.apache.samza.coordinator.JobModelManager.readJobModel(JobModelManager.scala)
	at org.apache.samza.standalone.StandaloneJobCoordinator.<init>(StandaloneJobCoordinator.java:108)
	at org.apache.samza.standalone.StandaloneJobCoordinatorFactory.getJobCoordinator(StandaloneJobCoordinatorFactory.java:29)
	at org.apache.samza.processor.StreamProcessor.<init>(StreamProcessor.java:111)
	at org.apache.samza.processor.StreamProcessor.<init>(StreamProcessor.java:94)
	at org.apache.samza.runtime.LocalApplicationRunner.createStreamProcessor(LocalApplicationRunner.java:231)
	at org.apache.samza.runtime.LocalApplicationRunner.lambda$run$0(LocalApplicationRunner.java:125)
	at org.apache.samza.runtime.LocalApplicationRunner$$Lambda$35/1940982718.accept(Unknown Source)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at org.apache.samza.runtime.LocalApplicationRunner.run(LocalApplicationRunner.java:121)
	... 2 more