Unhandled exception in the UI thread.

GAPID Version: 1.6.0:c0b6cac1c33fab1db1a9d3938201bea8ad581b45
OS: windows 10 amd64

Please provide detailed steps that led to the error and copy-paste the stack trace.
Extra details from the logs and the trace file would be extra helpful.

I was debugging a simple OpenGL cube application and I was trying the check the state of a frame. After clicking "DrawFrameBuffer", I have clicked one of the frames then one of the draw calls. Then I got this exception from the UI thread.

```
org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.NullPointerException)
at org.eclipse.swt.SWT.error(SWT.java:4595)
at org.eclipse.swt.SWT.error(SWT.java:4510)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:188)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3933)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3564)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:821)
at org.eclipse.jface.window.Window.open(Window.java:797)
at com.google.gapid.Main$UI.show(Main.java:119)
at com.google.gapid.Main.main(Main.java:68)
Caused by: java.lang.NullPointerException
at com.google.gapid.views.StateView.updateExpansionState(StateView.java:252)
at com.google.gapid.views.StateView.setExpanded(StateView.java:284)
at com.google.gapid.views.StateView$2.onUiThread(StateView.java:274)
at com.google.gapid.views.StateView$2.onUiThread(StateView.java:264)
at com.google.gapid.rpc.UiCallback.lambda$onFinish$0(UiCallback.java:46)
at com.google.gapid.widgets.Widgets.ifNotDisposed(Widgets.java:124)
at com.google.gapid.widgets.Widgets.lambda$scheduleIfNotDisposed$1(Widgets.java:152)
at com.google.gapid.widgets.Widgets.lambda$schedule$0(Widgets.java:144)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:40)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:185)
... 6 more
```