Fiji error stops the ability to edit files

[gbondy]

My files on fiji keep going dodgy and I can no longer delete treelines or connectors of anything and some of my connectors keep moving and turning up in random places. Can anybody help? I'm using fiji on mac. I get the error message

ERROR:
java.lang.NullPointerException
        at ini.trakem2.display.Displayable.toString(Displayable.java:1078)
        at ini.trakem2.tree.ProjectThing.toString(ProjectThing.java:224)
        at javax.swing.tree.DefaultMutableTreeNode.toString(DefaultMutableTreeNode.java:1229)
        at javax.swing.JTree.convertValueToText(JTree.java:1563)
        at javax.swing.tree.DefaultTreeCellRenderer.getTreeCellRendererComponent(DefaultTreeCellRenderer.java:346)
        at ini.trakem2.tree.DNDTree$NodeRenderer.getTreeCellRendererComponent(DNDTree.java:122)
        at ini.trakem2.tree.ProjectTree$ProjectThingNodeRenderer.getTreeCellRendererComponent(ProjectTree.java:761)
        at javax.swing.plaf.basic.BasicTreeUI$NodeDimensionsHandler.getNodeDimensions(BasicTreeUI.java:2712)
        at javax.swing.tree.AbstractLayoutCache.getNodeDimensions(AbstractLayoutCache.java:475)
        at javax.swing.tree.VariableHeightLayoutCache$TreeStateNode.updatePreferredSize(VariableHeightLayoutCache.java:1342)
        at javax.swing.tree.VariableHeightLayoutCache$TreeStateNode.expand(VariableHeightLayoutCache.java:1478)
        at javax.swing.tree.VariableHeightLayoutCache$TreeStateNode.expand(VariableHeightLayoutCache.java:1270)
        at javax.swing.tree.VariableHeightLayoutCache.ensurePathIsExpanded(VariableHeightLayoutCache.java:966)
        at javax.swing.tree.VariableHeightLayoutCache.setExpandedState(VariableHeightLayoutCache.java:164)
        at javax.swing.plaf.basic.BasicTreeUI.updateExpandedDescendants(BasicTreeUI.java:1650)
        at javax.swing.plaf.basic.BasicTreeUI.updateLayoutCacheExpandedNodes(BasicTreeUI.java:1632)
        at javax.swing.plaf.basic.BasicTreeUI.configureLayoutCache(BasicTreeUI.java:1769)
        at javax.swing.plaf.basic.BasicTreeUI.completeUIInstall(BasicTreeUI.java:670)
        at javax.swing.plaf.basic.BasicTreeUI.installUI(BasicTreeUI.java:630)
        at com.apple.laf.AquaTreeUI.installUI(AquaTreeUI.java:64)
        at javax.swing.JComponent.setUI(JComponent.java:670)
        at javax.swing.JTree.setUI(JTree.java:678)
        at javax.swing.JTree.updateUI(JTree.java:694)
        at ini.trakem2.tree.DNDTree$4.run(DNDTree.java:312)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:715)
        at java.awt.EventQueue.access$400(EventQueue.java:82)
        at java.awt.EventQueue$2.run(EventQueue.java:676)
        at java.awt.EventQueue$2.run(EventQueue.java:674)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:86)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:685)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)