Inspector: Fix compatibility with `WebGLBackend` if used as a fallback (#33019)

examples/jsm/inspector/Inspector.js

@@ -198,10 +198,10 @@ class Inspector extends RendererInspector {
 
 			if ( this.isAvailable ) {
 
-				renderer.backend.trackTimestamp = true;
-
 				renderer.init().then( () => {
 
+					renderer.backend.trackTimestamp = true;
+
 					if ( renderer.hasFeature( 'timestamp-query' ) !== true ) {
 
 						this.console.addMessage( 'error', 'THREE.Inspector: GPU Timestamp Queries not available.' );