Don't create tree node for Suspense with no fallback

No longer required now tracking DOM root with `domRootIndex`.

lib/renderer.js

@@ -262,21 +262,17 @@ class PartialRenderer extends ReactDOMServerRenderer {
 	}
 
 	handleSuspense(element) {
+		// If fallback is undefined, it's not treated as a suspense boundary
+		const {fallback} = element.props;
+		if (fallback === undefined) return;
+
 		// Add boundary node to tree and step into it
-		// NB If fallback is undefined, it's not treated as a suspense boundary
 		const frame = last(this.stack);
-
-		let node;
-		const {fallback} = element.props;
-		if (fallback !== undefined) {
-			node = this.createChildWithStackState(TYPE_SUSPENSE, frame);
-			node.fallback = fallback;
-			node.suspended = false;
-			this.suspenseNode = node;
-			this.suspended = false;
-		} else {
-			node = this.createChild(null);
-		}
+		const node = this.createChildWithStackState(TYPE_SUSPENSE, frame);
+		node.fallback = fallback;
+		node.suspended = false;
+		this.suspenseNode = node;
+		this.suspended = false;
 
 		this.node = node;