Fix compilation error

src/vs/base/browser/dom.ts

@@ -827,14 +827,18 @@ export function isShadowRoot(node: Node): node is ShadowRoot {
 }
 
 export function isInShadowDOM(domNode: Node): boolean {
+	return !!getShadowRoot(domNode);
+}
+
+export function getShadowRoot(domNode: Node): ShadowRoot | null {
 	while (domNode.parentNode) {
 		if (domNode === document.body) {
 			// reached the body
-			return false;
+			return null;
 		}
 		domNode = domNode.parentNode;
 	}
-	return isShadowRoot(domNode);
+	return isShadowRoot(domNode) ? domNode : null;
 }
 
 export function createStyleSheet(container: HTMLElement = document.getElementsByTagName('head')[0]): HTMLStyleElement {

src/vs/editor/contrib/codelens/codelensController.ts

@@ -68,7 +68,7 @@ export class CodeLensContribution implements IEditorContribution {
 		this._styleElement = dom.createStyleSheet(
 			dom.isInShadowDOM(this._editor.getContainerDomNode())
 				? this._editor.getContainerDomNode()
-				: null
+				: undefined
 		);
 		this._updateLensStyle();
 	}