[bugfix] Update selection box on entityupdate only if it's the selected entity

[vincentfretin]

This fixes an error when using undo with unselected entity so when inspector.selectedEntity can be undefined.

[vincentfretin]

This is a required change for undo feature @dmarcos
The condition is similar to the other entityupdate listener we have here

aframe-inspector/src/lib/viewport.js

Lines 182 to 184 in b792e91

	Events.on('entityupdate', (detail) => {
	const object = detail.entity.object3D;
	if (inspector.selected === object) {

[dmarcos]

Thanks so much!