java.lang.AssertionError: Should be a folder: C:\Users\Saptarshi\Documents\NetBeansProjects\WebApp\build\WEB-INF\classes\webapp@e1dd8a31:23fda199
   at org.netbeans.modules.masterfs.watcher.Watcher$Ext.unregister(Watcher.java:247)
   at org.netbeans.modules.masterfs.watcher.Watcher.unregister(Watcher.java:130)
   at org.netbeans.modules.masterfs.filebasedfs.fileobjects.BaseFileObj.removeFileChangeListener(BaseFileObj.java:508)
   at org.openide.filesystems.FileUtil$Holder.locateCurrent(FileUtil.java:434)
   at org.openide.filesystems.FileUtil$Holder.someChange(FileUtil.java:454)
   at org.openide.filesystems.FileUtil$Holder.fileDeleted(FileUtil.java:493)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEventImpl(FCLSupport.java:148)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEvent(FCLSupport.java:128)
   at org.openide.filesystems.FCLSupport.dispatchEvent(FCLSupport.java:105)
   at org.openide.filesystems.FileObject$ED.dispatch(FileObject.java:1165)
   at org.openide.filesystems.EventControl.invokeDispatchers(EventControl.java:213)
   at org.openide.filesystems.EventControl.exitAtomicAction(EventControl.java:188)
   at org.openide.filesystems.EventControl.runAtomicAction(EventControl.java:129)
   at org.openide.filesystems.FileSystem.runAtomicAction(FileSystem.java:566)
   at org.netbeans.modules.masterfs.filebasedfs.fileobjects.FileObjectFactory.refresh(FileObjectFactory.java:722)
   at org.netbeans.modules.masterfs.filebasedfs.fileobjects.RootObj.invokeRefreshFor(RootObj.java:197)
   at org.netbeans.modules.masterfs.filebasedfs.fileobjects.RootObj.invokeRefreshFor(RootObj.java:145)
   at org.netbeans.modules.masterfs.filebasedfs.fileobjects.RootObj.setAttribute(RootObj.java:138)
   at org.openide.filesystems.FileUtil.refreshFor(FileUtil.java:165)
   at org.openide.filesystems.FileUtil$1.run(FileUtil.java:188)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.AssertionError: Should be a folder: C:\Users\Saptarshi\Documents\NetBeansProjects\WebApp\build\WEB-INF\classes\webapp@e1dd8a31:23fda199
   at org.openide.util.RequestProcessor$Task.schedule(RequestProcessor.java:1465)
   at org.openide.filesystems.FileUtil.refreshAll(FileUtil.java:203)
   at org.apache.tools.ant.module.bridge.impl.BridgeImpl$1.run(BridgeImpl.java:324)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1973)