Update xml.browser.ts

Wrap policy-creation in try/catch

lib/util/xml.browser.ts

@@ -10,10 +10,14 @@ const parser = new DOMParser();
 // according to the spec.  There are no HTML/XSS security concerns on the usage of
 // parseFromString() here.
 let ttPolicy: Pick<TrustedTypePolicy, "createHTML"> | undefined;
-if (typeof self.trustedTypes !== "undefined") {
-  ttPolicy = self.trustedTypes.createPolicy("@azure/ms-rest-js#xml.browser", {
-    createHTML: (s) => s,
-  });
+try {
+  if (typeof self.trustedTypes !== "undefined") {
+    ttPolicy = self.trustedTypes.createPolicy("@azure/ms-rest-js#xml.browser", {
+      createHTML: (s) => s,
+    });
+  }
+} catch (e) {
+  console.warn('Could not create trusted types policy "@azure/ms-rest-js#xml.browser"');
 }
 
 export function parseXML(str: string): Promise<any> {