Dataflow streaming runner fails SDF testWindowedSideInputWithCheckpoints

When testing https://github.com/apache/beam/pull/1898

INFO: 2017-06-20T00:04:36.310Z: (22acf084264efa8): Executing operation PAssert$7/GroupGlobally/GroupDummyAndContents/ReadStream****PAssert$7/GroupGlobally/GroupDummyAndContents/MergeBuckets****PAssert$7/GroupGlobally/Values/Values/Map****PAssert$7/GroupGlobally/ParDo(Concat)****PAssert$7/GetPane/Map****PAssert$7/RunChecks****PAssert$7/VerifyAssertions/ParDo(DefaultConclude)
Jun 19, 2017 5:04:59 PM org.apache.beam.runners.dataflow.util.MonitoringUtil$LoggingHandler process
SEVERE: 2017-06-20T00:04:58.641Z: (6a9da772bd8097d0): java.lang.RuntimeException: Exception while fetching side input:
com.google.cloud.dataflow.worker.runners.worker.StateFetcher.fetchSideInput(StateFetcher.java:182)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext.fetchSideInput(StreamingModeExecutionContext.java:211)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext.access$700(StreamingModeExecutionContext.java:70)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext$StepContext.issueSideInputFetch(StreamingModeExecutionContext.java:572)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext$UserStepContext.issueSideInputFetch(StreamingModeExecutionContext.java:624)
com.google.cloud.dataflow.worker.runners.worker.StreamingSideInputFetcher.getReadyWindows(StreamingSideInputFetcher.java:136)
com.google.cloud.dataflow.worker.runners.worker.StreamingSideInputDoFnRunner.startBundle(StreamingSideInputDoFnRunner.java:51)
com.google.cloud.dataflow.worker.runners.worker.SimpleParDoFn.reallyStartBundle(SimpleParDoFn.java:222)
com.google.cloud.dataflow.worker.runners.worker.SimpleParDoFn.startBundle(SimpleParDoFn.java:150)
com.google.cloud.dataflow.worker.runners.worker.ForwardingParDoFn.startBundle(ForwardingParDoFn.java:36)
com.google.cloud.dataflow.worker.util.common.worker.ParDoOperation.start(ParDoOperation.java:40)
com.google.cloud.dataflow.worker.util.common.worker.MapTaskExecutor.execute(MapTaskExecutor.java:69)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker.process(StreamingDataflowWorker.java:977)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker.access$800(StreamingDataflowWorker.java:127)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker$7.run(StreamingDataflowWorker.java:761)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)
Caused by: com.google.cloud.dataflow.worker.repackaged.com.google.common.util.concurrent.UncheckedExecutionException: java.util.NoSuchElementException: Empty PCollection accessed as a singleton view.
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2214)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache.get(LocalCache.java:4053)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4899)
com.google.cloud.dataflow.worker.runners.worker.StateFetcher.fetchSideInput(StateFetcher.java:173)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext.fetchSideInput(StreamingModeExecutionContext.java:211)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext.access$700(StreamingModeExecutionContext.java:70)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext$StepContext.issueSideInputFetch(StreamingModeExecutionContext.java:572)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext$UserStepContext.issueSideInputFetch(StreamingModeExecutionContext.java:624)
com.google.cloud.dataflow.worker.runners.worker.StreamingSideInputFetcher.getReadyWindows(StreamingSideInputFetcher.java:136)
com.google.cloud.dataflow.worker.runners.worker.StreamingSideInputDoFnRunner.startBundle(StreamingSideInputDoFnRunner.java:51)
com.google.cloud.dataflow.worker.runners.worker.SimpleParDoFn.reallyStartBundle(SimpleParDoFn.java:222)
com.google.cloud.dataflow.worker.runners.worker.SimpleParDoFn.startBundle(SimpleParDoFn.java:150)
com.google.cloud.dataflow.worker.runners.worker.ForwardingParDoFn.startBundle(ForwardingParDoFn.java:36)
com.google.cloud.dataflow.worker.util.common.worker.ParDoOperation.start(ParDoOperation.java:40)
com.google.cloud.dataflow.worker.util.common.worker.MapTaskExecutor.execute(MapTaskExecutor.java:69)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker.process(StreamingDataflowWorker.java:977)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker.access$800(StreamingDataflowWorker.java:127)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker$7.run(StreamingDataflowWorker.java:761)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)
Caused by: java.util.NoSuchElementException: Empty PCollection accessed as a singleton view.
org.apache.beam.sdk.values.PCollectionViews$SingletonViewFn.getDefaultValue(PCollectionViews.java:190)
org.apache.beam.sdk.values.PCollectionViews$SingletonViewFn.apply(PCollectionViews.java:215)
org.apache.beam.sdk.values.PCollectionViews$SingletonViewFn.apply(PCollectionViews.java:151)
com.google.cloud.dataflow.worker.runners.worker.StateFetcher$2.call(StateFetcher.java:150)
com.google.cloud.dataflow.worker.runners.worker.StateFetcher$2.call(StateFetcher.java:105)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$LocalManualCache$1.load(LocalCache.java:4904)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3628)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2336)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2295)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2208)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache.get(LocalCache.java:4053)
com.google.cloud.dataflow.worker.repackaged.com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4899)
com.google.cloud.dataflow.worker.runners.worker.StateFetcher.fetchSideInput(StateFetcher.java:173)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext.fetchSideInput(StreamingModeExecutionContext.java:211)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext.access$700(StreamingModeExecutionContext.java:70)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext$StepContext.issueSideInputFetch(StreamingModeExecutionContext.java:572)
com.google.cloud.dataflow.worker.runners.worker.StreamingModeExecutionContext$UserStepContext.issueSideInputFetch(StreamingModeExecutionContext.java:624)
com.google.cloud.dataflow.worker.runners.worker.StreamingSideInputFetcher.getReadyWindows(StreamingSideInputFetcher.java:136)
com.google.cloud.dataflow.worker.runners.worker.StreamingSideInputDoFnRunner.startBundle(StreamingSideInputDoFnRunner.java:51)
com.google.cloud.dataflow.worker.runners.worker.SimpleParDoFn.reallyStartBundle(SimpleParDoFn.java:222)
com.google.cloud.dataflow.worker.runners.worker.SimpleParDoFn.startBundle(SimpleParDoFn.java:150)
com.google.cloud.dataflow.worker.runners.worker.ForwardingParDoFn.startBundle(ForwardingParDoFn.java:36)
com.google.cloud.dataflow.worker.util.common.worker.ParDoOperation.start(ParDoOperation.java:40)
com.google.cloud.dataflow.worker.util.common.worker.MapTaskExecutor.execute(MapTaskExecutor.java:69)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker.process(StreamingDataflowWorker.java:977)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker.access$800(StreamingDataflowWorker.java:127)
com.google.cloud.dataflow.worker.runners.worker.StreamingDataflowWorker$7.run(StreamingDataflowWorker.java:761)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)

Imported from Jira [BEAM-2476](https://issues.apache.org/jira/browse/BEAM-2476). Original Jira may contain additional context.
Reported by: jkff.

Start with the Dataflow streaming runner test named testWindowedSideInputWithCheckpoints and reproduce the failure described in the stack trace. Read StreamingSideInputFetcher, StreamingModeExecutionContext, StateFetcher, and PCollectionViews.SingletonViewFn; done means the test completes without the Empty PCollection singleton-view exception.

Written by the indexing model from the issue text.