If you install the G1 Page plugin and open a recording without the required events, and then click the page, you will get a modal error dialog on top of JMC. "Page could not display data" is the title, "The page cannot be shown correctly for this recording. The recording may be from an old JVM, or invalid in some other way" is the description and the details are as follows:

java.lang.IndexOutOfBoundsException: Index: 0
at java.util.Collections$EmptyList.get(Collections.java:4463)
at com.oracle.jmc.flightrecorder.ext.g1.G1Page$G1PageUI.setUpHeapDumps(G1Page.java:431)
at com.oracle.jmc.flightrecorder.ext.g1.G1Page$G1PageUI.<init>(G1Page.java:188)
at com.oracle.jmc.flightrecorder.ext.g1.G1Page.display(G1Page.java:587)
at com.oracle.jmc.flightrecorder.ui.JfrEditor.displayPage(JfrEditor.java:171)
at com.oracle.jmc.flightrecorder.ui.JfrEditor.navigateTo(JfrEditor.java:154)
at com.oracle.jmc.flightrecorder.ui.JfrOutlinePage.selectionChanged(JfrOutlinePage.java:393)
at org.eclipse.jface.viewers.Viewer$2.run(Viewer.java:163)
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:173)
at org.eclipse.jface.viewers.Viewer.fireSelectionChanged(Viewer.java:160)
at org.eclipse.jface.viewers.StructuredViewer.updateSelection(StructuredViewer.java:2197)
at org.eclipse.jface.viewers.StructuredViewer.handleSelect(StructuredViewer.java:1228)
at org.eclipse.jface.viewers.StructuredViewer$4.widgetSelected(StructuredViewer.java:1257)
at org.eclipse.jface.util.OpenStrategy.fireSelectionEvent(OpenStrategy.java:242)
at org.eclipse.jface.util.OpenStrategy.access$4(OpenStrategy.java:236)
at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:408)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4362)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1113)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4180)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3769)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1127)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1018)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:156)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:654)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:598)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at com.oracle.jmc.rcp.application.Application.start(Application.java:36)
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:520)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:669)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:608)
at org.eclipse.equinox.launcher.Main.run(Main.java:1515)
at org.eclipse.equinox.launcher.Main.main(Main.java:1488)