I encountered this issue while trying to verify TEIIDDES-2520.

When you have no server started in TD. Action Create Source model from Teiid data source DDL in Guides causes NPE.

Screenshot attached

Problems occurred when invoking code from plug-in: "org.eclipse.jface".

org.eclipse.core.runtime.AssertionFailedException: null argument:
at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:85)
at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:73)
at org.teiid.designer.ui.common.wizard.AbstractWizard.createPageControls(AbstractWizard.java:156)
at org.teiid.designer.ui.common.wizard.AbstractWizard.createPageControls(AbstractWizard.java:138)
at org.teiid.designer.teiidimporter.ui.wizard.TeiidImportWizard.createPageControls(TeiidImportWizard.java:181)
at org.eclipse.jface.wizard.WizardDialog.createPageControls(WizardDialog.java:759)
at org.eclipse.jface.wizard.WizardDialog.createContents(WizardDialog.java:622)
at org.eclipse.jface.window.Window.create(Window.java:435)
at org.eclipse.jface.dialogs.Dialog.create(Dialog.java:1101)
at org.teiid.designer.ui.viewsupport.ModelerUiViewUtils$7.run(ModelerUiViewUtils.java:250)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:187)
at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:156)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4734)
at org.teiid.designer.ui.viewsupport.ModelerUiViewUtils.launchWizard(ModelerUiViewUtils.java:240)
at org.teiid.designer.ui.viewsupport.ModelerUiViewUtils$5.run(ModelerUiViewUtils.java:185)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:187)
at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:156)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4734)
at org.teiid.designer.ui.viewsupport.ModelerUiViewUtils.launchWizard(ModelerUiViewUtils.java:167)
at org.teiid.designer.advisor.ui.actions.AdvisorActionFactory.launchWizard(AdvisorActionFactory.java:913)
at org.teiid.designer.advisor.ui.actions.AdvisorActionFactory.executeAction(AdvisorActionFactory.java:470)
at org.teiid.designer.advisor.ui.views.guides.TeiidGuidesSection.launchGuidesAction(TeiidGuidesSection.java:281)
at org.teiid.designer.advisor.ui.views.guides.TeiidGuidesSection.access$1(TeiidGuidesSection.java:271)
at org.teiid.designer.advisor.ui.views.guides.TeiidGuidesSection$4.doubleClick(TeiidGuidesSection.java:174)
at org.eclipse.jface.viewers.StructuredViewer$1.run(StructuredViewer.java:831)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:50)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:178)
at org.eclipse.jface.viewers.StructuredViewer.fireDoubleClick(StructuredViewer.java:828)
at org.eclipse.jface.viewers.AbstractTreeViewer.handleDoubleSelect(AbstractTreeViewer.java:1472)
at org.eclipse.jface.viewers.StructuredViewer$4.widgetDefaultSelected(StructuredViewer.java:1237)
at org.eclipse.jface.util.OpenStrategy.fireDefaultSelectionEvent(OpenStrategy.java:252)
at org.eclipse.jface.util.OpenStrategy.access$0(OpenStrategy.java:249)
at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:311)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4353)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1061)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4172)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3761)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1151)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1032)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:148)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:636)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:579)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:135)
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:380)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:235)
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:483)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:648)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:603)
at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
at org.eclipse.equinox.launcher.Main.main(Main.java:1438)