Add guard around location redirect.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "umami",
-  "version": "1.39.0-beta.1",
+  "version": "1.39.0-beta.2",
   "description": "A simple, fast, privacy-focused alternative to Google Analytics.",
   "author": "Mike Cao <mike@mikecao.com>",
   "license": "MIT",

tracker/index.js

@@ -143,7 +143,10 @@
             ) {
               e.preventDefault();
               trackEvent(name).then(() => {
-                location.href = get('href');
+                const href = get('href');
+                if (href) {
+                  location.href = href;
+                }
               });
             } else {
               trackEvent(name);