I looked into it and found the following exception:
!ENTRY org.eclipse.ui 4 0 2018-12-07 09:06:54.829
!MESSAGE Unhandled event loop exception
!STACK 0
org.eclipse.swt.SWTError: No more handles
at org.eclipse.swt.SWT.error(SWT.java:4559)
at org.eclipse.swt.SWT.error(SWT.java:4448)
at org.eclipse.swt.SWT.error(SWT.java:4419)
at org.eclipse.swt.widgets.Display.error(Display.java:1263)
at org.eclipse.swt.widgets.Display.internal_new_GC(Display.java:2708)
at org.eclipse.swt.graphics.Device.getDepth(Device.java:454)
at org.eclipse.swt.custom.CTabFolder.setBackground(CTabFolder.java:2409)
at org.eclipse.e4.ui.css.swt.properties.custom.CSSPropertyUnselectedTabsSWTHandler.applyCSSProperty(CSSPropertyUnselectedTabsSWTHandler.java:71)
at org.eclipse.e4.ui.css.swt.properties.AbstractCSSPropertySWTHandler.applyCSSProperty(AbstractCSSPropertySWTHandler.java:32)
at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyCSSProperty(AbstractCSSEngine.java:766)
at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyleDeclaration(AbstractCSSEngine.java:552)
at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyles(AbstractCSSEngine.java:418)
at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyles(AbstractCSSEngine.java:367)
at org.eclipse.e4.ui.css.swt.internal.theme.ThemeEngine.applyStyles(ThemeEngine.java:507)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.setClassnameAndId(PartRenderingEngine.java:1322)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.setCSSInfo(SWTPartRenderer.java:111)
at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.updateNonFocusState(WBWRenderer.java:662)
at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.lambda$4(WBWRenderer.java:632)
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.Decorations.WM_ACTIVATE(Decorations.java:1698)
at org.eclipse.swt.widgets.Shell.WM_ACTIVATE(Shell.java:2277)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4840)
at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:359)
at org.eclipse.swt.widgets.Decorations.windowProc(Decorations.java:1657)
at org.eclipse.swt.widgets.Shell.windowProc(Shell.java:2199)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:5191)
at org.eclipse.swt.internal.win32.OS.DefWindowProcW(Native Method)
at org.eclipse.swt.internal.win32.OS.DefWindowProc(OS.java:2555)
at org.eclipse.swt.widgets.Shell.callWindowProc(Shell.java:506)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4941)
at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:359)
at org.eclipse.swt.widgets.Decorations.windowProc(Decorations.java:1657)
at org.eclipse.swt.widgets.Shell.windowProc(Shell.java:2199)
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.knime.product.rcp.KNIMEApplication.start(KNIMEApplication.java:144)
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(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
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)
Could this be a possible reason? I attached the entire log file.log.txt (990.1 KB)