Fix: signOutTargetUrl determination

Signed-off-by: Gabriel Huber <mail@ghuber.de>

.changeset/empty-clocks-argue.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core-app-api': patch
+---
+
+Fixed bug in AppRouter to determine the correct signOutTargetUrl if app.baseUrl contains a basePath

packages/core-app-api/src/app/AppRouter.tsx

@@ -70,7 +70,7 @@ function SignInPageWrapper({
 }) {
   const [identityApi, setIdentityApi] = useState<IdentityApi>();
   const configApi = useApi(configApiRef);
-  const basePath = getBasePath(configApi);
+  const basePath = readBasePath(configApi);
 
   if (!identityApi) {
     return <Component onSignInSuccess={setIdentityApi} />;