为什么我在Eclipse中的动态Web项目中出现此错误？

即使我的程序正在运行，我也有此错误消息 .

从插件调用代码时出现问题： "org.eclipse.jface" .

异常堆栈跟踪：

java.lang.NullPointerException
    at org.eclipse.jst.jee.ui.internal.navigator.web.WebAppProvider.getImage(WebAppProvider.java:100)
    at org.eclipse.jst.jee.ui.internal.navigator.Web25LabelProvider.getImage(Web25LabelProvider.java:47)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceLabelProvider.findImage(NavigatorContentServiceLabelProvider.java:199)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceLabelProvider.getColumnImage(NavigatorContentServiceLabelProvider.java:107)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceLabelProvider.getImage(NavigatorContentServiceLabelProvider.java:99)
    at org.eclipse.ui.internal.navigator.NavigatorDecoratingLabelProvider$StyledLabelProviderAdapter.getImage(NavigatorDecoratingLabelProvider.java:57)
    at org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider.getImage(DelegatingStyledCellLabelProvider.java:195)
    at org.eclipse.jface.viewers.DecoratingStyledCellLabelProvider.getImage(DecoratingStyledCellLabelProvider.java:168)
    at org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider.update(DelegatingStyledCellLabelProvider.java:121)
    at org.eclipse.jface.viewers.DecoratingStyledCellLabelProvider.update(DecoratingStyledCellLabelProvider.java:131)
    at org.eclipse.jface.viewers.ViewerColumn.refresh(ViewerColumn.java:141)
    at org.eclipse.jface.viewers.AbstractTreeViewer.doUpdateItem(AbstractTreeViewer.java:946)
    at org.eclipse.jface.viewers.AbstractTreeViewer$UpdateItemSafeRunnable.run(AbstractTreeViewer.java:117)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.JFaceUtil.lambda$0(JFaceUtil.java:44)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:173)
    at org.eclipse.jface.viewers.AbstractTreeViewer.doUpdateItem(AbstractTreeViewer.java:1025)
    at org.eclipse.jface.viewers.StructuredViewer$UpdateItemSafeRunnable.run(StructuredViewer.java:475)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.JFaceUtil.lambda$0(JFaceUtil.java:44)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:173)
    at org.eclipse.jface.viewers.StructuredViewer.updateItem(StructuredViewer.java:2159)
    at org.eclipse.jface.viewers.AbstractTreeViewer.createTreeItem(AbstractTreeViewer.java:840)
    at org.eclipse.jface.viewers.AbstractTreeViewer.lambda$0(AbstractTreeViewer.java:817)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:792)
    at org.eclipse.jface.viewers.TreeViewer.createChildren(TreeViewer.java:595)
    at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:763)
    at org.eclipse.jface.viewers.AbstractTreeViewer.handleTreeExpand(AbstractTreeViewer.java:1482)
    at org.eclipse.jface.viewers.TreeViewer.handleTreeExpand(TreeViewer.java:880)
    at org.eclipse.jface.viewers.AbstractTreeViewer$3.treeExpanded(AbstractTreeViewer.java:1494)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:133)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:86)
    at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4428)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1103)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1088)
    at org.eclipse.swt.widgets.Tree.wmNotifyChild(Tree.java:7819)
    at org.eclipse.swt.widgets.Control.wmNotify(Control.java:5869)
    at org.eclipse.swt.widgets.Composite.wmNotify(Composite.java:2025)
    at org.eclipse.swt.widgets.Control.WM_NOTIFY(Control.java:5423)
    at org.eclipse.swt.widgets.Control.windowProc(Control.java:4899)
    at org.eclipse.swt.widgets.Display.windowProc(Display.java:5178)
    at org.eclipse.swt.internal.win32.OS.CallWindowProcW(Native Method)
    at org.eclipse.swt.internal.win32.OS.CallWindowProc(OS.java:2454)
    at org.eclipse.swt.widgets.Tree.callWindowProc(Tree.java:1555)
    at org.eclipse.swt.widgets.Tree.WM_LBUTTONDOWN(Tree.java:6673)
    at org.eclipse.swt.widgets.Control.windowProc(Control.java:4879)
    at org.eclipse.swt.widgets.Tree.windowProc(Tree.java:6188)
    at org.eclipse.swt.widgets.Display.windowProc(Display.java:5178)
    at org.eclipse.swt.internal.win32.OS.DispatchMessageW(Native Method)
    at org.eclipse.swt.internal.win32.OS.DispatchMessage(OS.java:2560)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3815)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1150)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1039)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
    at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:680)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:594)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:653)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:590)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1499)