fix(ui): wait for podcast object to be available before checking if we can see it

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2465>

changes/changelog.d/2155.bugfix

@@ -0,0 +1 @@
+Fixed premature login redirect on podcast detail page (#2155)

front/src/views/channels/DetailBase.vue

@@ -103,7 +103,8 @@ watch([uuid, object], ([uuid, object], [lastUuid, lastObject]) => {
 
 const route = useRoute()
 watchEffect(() => {
-  if (!store.state.auth.authenticated && store.getters['instance/domain'] !== object.value?.actor.domain) {
+  if (!object.value) return
+  if (!store.state.auth.authenticated && store.getters['instance/domain'] !== object.value.actor.domain) {
     router.push({ name: 'login', query: { next: route.fullPath } })
   }
 })