test(common): change fallback default URL in MockPlatformLocation (#4…

…4211)

In node@16 the URL constructor fails for for a malformed URL such as http://<empty>/. Instead http://_empty_ is
used as this conveys the same information in tests but is correctly formed.

PR Close #44211

packages/common/testing/src/mock_platform_location.ts

@@ -122,7 +122,7 @@ export class MockPlatformLocation implements PlatformLocation {
       this.baseHref = config.appBaseHref || '';
 
       const parsedChanges =
-          this.parseChanges(null, config.startUrl || 'http://<empty>/', this.baseHref);
+          this.parseChanges(null, config.startUrl || 'http://_empty_/', this.baseHref);
       this.urlChanges[0] = {...parsedChanges};
     }
   }