java.lang.NullPointerException: 
   at ent.EntityClasses.Storage.toString(Storage.java:111)
   at se.dfx.simplesql.EntityManagerImpl.performPersist(EntityManagerImpl.java:332)
   at se.dfx.simplesql.EntityManagerImpl.merge(EntityManagerImpl.java:81)
   at se.dfx.simplesql.EntityManagerImpl.persist(EntityManagerImpl.java:40)
   at rmiserver.ent.manager.AbstractRegManager.persist(AbstractRegManager.java:109)
   at rmiserver.ent.manager.storageRegManager.setInt(storageRegManager.java:89)
   at rmiserver.ent.manager.storageRegManager.setBoolean(storageRegManager.java:112)
   at rmiserver.Maintenance.setInMaintenanceFlag(Maintenance.java:72)
   at rmiserver.Maintenance.run(Maintenance.java:60)
Caused: org.netbeans.api.debugger.jpda.InvalidExpressionException: Exception occurred in target VM: 
   at org.netbeans.modules.debugger.jpda.expr.TreeEvaluator.invokeVirtual(TreeEvaluator.java:283)
   at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.invokeMethod(JPDADebuggerImpl.java:1014)
   at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.invokeMethod(JPDADebuggerImpl.java:950)
   at org.netbeans.modules.debugger.jpda.models.AbstractObjectVariable.getToStringValue(AbstractObjectVariable.java:476)
   at org.netbeans.modules.debugger.jpda.models.AbstractObjectVariable.getToStringValue(AbstractObjectVariable.java:425)
Caused: java.lang.reflect.InvocationTargetException
   at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:0)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:601)
   at org.netbeans.modules.debugger.jpda.ui.models.VariablesNodeModel.getLimitedToString(VariablesNodeModel.java:342)
   at org.netbeans.modules.debugger.jpda.ui.models.VariablesNodeModel.getShortDescriptionSynch(VariablesNodeModel.java:291)
   at org.netbeans.modules.debugger.jpda.ui.models.WatchesNodeModelFilter.getShortDescriptionSynch(WatchesNodeModelFilter.java:139)
   at org.netbeans.modules.debugger.jpda.ui.models.VariablesNodeModel$1.run(VariablesNodeModel.java:264)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1454)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2048)