InMemorySessionStore throws NullPointerException on startup

I receive a NullPointerException on startup when trying to use the new InMemorySessionStore via Stores.inMemorySessionStore(...) using the DSL.

Here's the stack trace:

ERROR [2019-07-29 21:56:52,246] org.apache.kafka.streams.processor.internals.StreamThread: stream-thread [trace_indexer-c8439020-12af-4db2-ad56-3e58cd56540f-StreamThread-1] Encountered the following error during processing:
! java.lang.NullPointerException: null
! at org.apache.kafka.streams.state.internals.InMemorySessionStore.remove(InMemorySessionStore.java:123)
! at org.apache.kafka.streams.state.internals.InMemorySessionStore.put(InMemorySessionStore.java:115)
! at org.apache.kafka.streams.state.internals.InMemorySessionStore.lambda$init$0(InMemorySessionStore.java:93)
! at org.apache.kafka.streams.processor.internals.StateRestoreCallbackAdapter.lambda$adapt$1(StateRestoreCallbackAdapter.java:47)
! at org.apache.kafka.streams.processor.internals.CompositeRestoreListener.restoreBatch(CompositeRestoreListener.java:89)
! at org.apache.kafka.streams.processor.internals.StateRestorer.restore(StateRestorer.java:92)
! at org.apache.kafka.streams.processor.internals.StoreChangelogReader.processNext(StoreChangelogReader.java:317)
! at org.apache.kafka.streams.processor.internals.StoreChangelogReader.restore(StoreChangelogReader.java:92)
! at org.apache.kafka.streams.processor.internals.TaskManager.updateNewAndRestoringTasks(TaskManager.java:328)
! at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:867)
! at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:805)
! at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:774)

Here's the Slack thread:

https://confluentcommunity.slack.com/archives/C48AHTCUQ/p1564438647169600

Here's a current PR aimed at fixing the issue:

https://github.com/apache/kafka/pull/7132