HDR Sandcastle crashes when log depth is off

[lilleyse]

Sandcastle - click the HDR button to disable HDR. Then it crashes with this message:

An error occurred while rendering. Rendering has stopped.
TypeError: Cannot read property 'execute' of undefined
TypeError: Cannot read property 'execute' of undefined
at executeCommand (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:244061:60)
at executeCommands (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:244427:17)
at executeCommandsInViewport (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:244840:9)
at updateAndExecuteCommands (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:244633:13)
at render (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:245284:9)
at tryAndCatchError (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:245304:13)
at Scene.render (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:245375:13)
at CesiumWidget.render (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:259308:25)
at render (https://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js:258679:32)

[jjhembd]

Duplicate of #8372.