Exceptions and superposition failure when viewing PDB files with empty chain codes in Chimera

PDB files produced by modelling tools often lack PDB chain codes (like the one attached). Importing these to view in Chimera yields the following exception:

Time for creating model: 68 ms
Exception in thread "Thread-132" java.lang.NullPointerException
        at java.util.Collections.sort(Collections.java:175)
        at jalview.ext.rbvi.chimera.AtomSpecModel.getAtomSpec(AtomSpecModel.java:130)
        at jalview.ext.rbvi.chimera.ChimeraCommands.buildColourCommands(ChimeraCommands.java:121)
        at jalview.ext.rbvi.chimera.ChimeraCommands.getColourBySequenceCommand(ChimeraCommands.java:75)
        at jalview.ext.rbvi.chimera.JalviewChimeraBinding.getColourBySequenceCommands(JalviewChimeraBinding.java:701)
        at jalview.structures.models.AAStructureBindingModel.colourBySequence(AAStructureBindingModel.java:814)
        at jalview.gui.JalviewChimeraBindingModel.updateColours(JalviewChimeraBindingModel.java:90)
        at jalview.gui.ChimeraViewFrame.run(ChimeraViewFrame.java:638)
        at java.lang.Thread.run(Thread.java:745)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at java.util.Collections.sort(Collections.java:175)
        at jalview.ext.rbvi.chimera.AtomSpecModel.getAtomSpec(AtomSpecModel.java:130)
        at jalview.ext.rbvi.chimera.ChimeraCommands.buildColourCommands(ChimeraCommands.java:121)
        at jalview.ext.rbvi.chimera.ChimeraCommands.getColourBySequenceCommand(ChimeraCommands.java:75)
        at jalview.ext.rbvi.chimera.JalviewChimeraBinding.getColourBySequenceCommands(JalviewChimeraBinding.java:701)
        at jalview.structures.models.AAStructureBindingModel.colourBySequence(AAStructureBindingModel.java:814)
        at jalview.gui.StructureViewerBase.seqColour_actionPerformed(StructureViewerBase.java:906)
        at jalview.gui.StructureViewerBase.updateTitleAndMenus(StructureViewerBase.java:1024)
        at jalview.gui.JalviewChimeraBindingModel$1.run(JalviewChimeraBindingModel.java:73)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
        at java.awt.EventQueue.access$500(EventQueue.java:97)
        at java.awt.EventQueue$3.run(EventQueue.java:709)
        at java.awt.EventQueue$3.run(EventQueue.java:703)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)