sts4: STS4 Does Not Start After Installing Papyrus Plugin

Absolutely new installation of STS 4.7.0 does not start anymore after installing Payrus for UML plugin v. 4.8.0.202006100749. Attached is log file that was generated in STS workspace folder. From the log we can see that the root cause exception is :

!ENTRY org.eclipse.osgi 4 0 2020-07-02 00:33:11.207
!MESSAGE Application error
!STACK 1
java.lang.NullPointerException
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1091)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1047)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
	at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:658)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:557)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:154)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:150)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
	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:657)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1447)

!ENTRY org.eclipse.gmf.runtime.common.ui 4 0 2020-07-02 00:33:11.262
!MESSAGE FrameworkEvent ERROR
!STACK 0
org.osgi.framework.BundleException: Exception in org.eclipse.gmf.runtime.common.ui.internal.CommonUIPlugin.stop() of bundle org.eclipse.gmf.runtime.common.ui.
	at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(BundleContextImpl.java:920)
	at org.eclipse.osgi.internal.framework.EquinoxBundle.stopWorker0(EquinoxBundle.java:1029)
	at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.stopWorker(EquinoxBundle.java:370)
	at org.eclipse.osgi.container.Module.doStop(Module.java:660)
	at org.eclipse.osgi.container.Module.stop(Module.java:521)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.decStartLevel(ModuleContainer.java:1886)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(ModuleContainer.java:1761)
	at org.eclipse.osgi.container.SystemModule.stopWorker(SystemModule.java:275)
	at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule.stopWorker(EquinoxBundle.java:202)
	at org.eclipse.osgi.container.Module.doStop(Module.java:660)
	at org.eclipse.osgi.container.Module.stop(Module.java:521)
	at org.eclipse.osgi.container.SystemModule.stop(SystemModule.java:207)
	at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule$1.run(EquinoxBundle.java:220)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
	at org.eclipse.gmf.runtime.common.ui.util.UIModificationValidator.dispose(UIModificationValidator.java:208)
	at org.eclipse.gmf.runtime.common.ui.internal.CommonUIPlugin.stop(CommonUIPlugin.java:84)
	at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:900)
	at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:1)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(BundleContextImpl.java:892)
	... 13 more
Root exception:
java.lang.NullPointerException
	at org.eclipse.gmf.runtime.common.ui.util.UIModificationValidator.dispose(UIModificationValidator.java:208)
	at org.eclipse.gmf.runtime.common.ui.internal.CommonUIPlugin.stop(CommonUIPlugin.java:84)
	at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:900)
	at org.eclipse.osgi.internal.framework.BundleContextImpl$4.run(BundleContextImpl.java:1)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(BundleContextImpl.java:892)
	at org.eclipse.osgi.internal.framework.EquinoxBundle.stopWorker0(EquinoxBundle.java:1029)
	at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.stopWorker(EquinoxBundle.java:370)
	at org.eclipse.osgi.container.Module.doStop(Module.java:660)
	at org.eclipse.osgi.container.Module.stop(Module.java:521)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.decStartLevel(ModuleContainer.java:1886)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(ModuleContainer.java:1761)
	at org.eclipse.osgi.container.SystemModule.stopWorker(SystemModule.java:275)
	at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule.stopWorker(EquinoxBundle.java:202)
	at org.eclipse.osgi.container.Module.doStop(Module.java:660)
	at org.eclipse.osgi.container.Module.stop(Module.java:521)
	at org.eclipse.osgi.container.SystemModule.stop(SystemModule.java:207)
	at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule$1.run(EquinoxBundle.java:220)
	at java.lang.Thread.run(Unknown Source)

sts4.log