jbpm-console throws null pointer reading process instance

We had an issue where we had deployed a workflow without deploying the corresponding task definitions properly (CustomWorkItemHandlers.conf). This caused a couple of entries to appear in the processinstanceinfo table in the database with no processinstancebytearray, and the code doesn't protect itself from there being a null bytearray in the db. See null pointer exception below, found when trying to pull up the workflow in the console.

Caused by: java.lang.NullPointerException
        at java.io.ByteArrayInputStream.<init>(ByteArrayInputStream.java:106) [rt.jar:1.7.0_03]
        at org.jbpm.persistence.processinstance.ProcessInstanceInfo.getProcessInstance(ProcessInstanceInfo.java:132) [jbpm-persistence-jpa-5.4.0-SNAPSHOT.jar:5.4.0-SNAPSHOT]

The symptoms of the problem are the following:

1. Start a fresh instance of jBPM 5.4 from installer
2. Log on to console to make sure evaluation process is available and task server is accessible (no errors on task panels)
3. Stop/Undeploy jbpm-human-task-server.war
4. Start evaluation process
5. A NPE occurs.
6. Trying to start another instance of the same process results in an NPE because of the logic involved with getting existing running processes.