Experiment overview is broken if protocols with non-predefined protocol types are used

[Nicklas Nordborg]

A predefined protocol type is a protocol type which has a system ID. It is indicated with a "lock" icon in the Administrate -> Protocol types list. The only known workaround is to use protocols with the predefined protocol types.

Here is the stack trace:

java.lang.NullPointerException
...at net.sf.basedb.util.overview.ExperimentOverview.addProtocol(ExperimentOverview.java:1502)
...at net.sf.basedb.util.overview.ExperimentOverview.addSample(ExperimentOverview.java:1145)
...at net.sf.basedb.util.overview.ExperimentOverview.addExtract(ExperimentOverview.java:1039)
...at net.sf.basedb.util.overview.ExperimentOverview.addLabeledExtract(ExperimentOverview.java:914)
...at net.sf.basedb.util.overview.ExperimentOverview.addLabeledExtracts(ExperimentOverview.java:841)
...at net.sf.basedb.util.overview.ExperimentOverview.addHybridization(ExperimentOverview.java:781)
...at net.sf.basedb.util.overview.ExperimentOverview.addScan(ExperimentOverview.java:748)
...at net.sf.basedb.util.overview.ExperimentOverview.addRawBioAssay(ExperimentOverview.java:604)

...at net.sf.basedb.util.overview.ExperimentOverview.addRawBioAssays(ExperimentOverview.java:580)
...at net.sf.basedb.util.overview.ExperimentOverview.generateOverview(ExperimentOverview.java:316)
...at net.sf.basedb.util.overview.ExperimentOverview.<init>(ExperimentOverview.java:257)
...at net.sf.basedb.util.overview.ExperimentOverview.getOverview(ExperimentOverview.java:188)
...at org.apache.jsp.views.experiments.overview.index_jsp._jspService(index_jsp.java:87)

The NullPointerException happens beacuse ProtocolType.getSystemId() return null.

[Nicklas Nordborg]

(In [3825]) Fixes #803: Experiment overview is broken if protocols with non-predefined protocol types are used