Leave playlist/collection detail pages when the library changes (#1711, #1712)

The item detail page already listens for the app-wide `library-changed`
event and navigates away; the playlist and collection detail pages did
not, so switching libraries left them showing stale content with no way
back to the list.

- playlist/_id.vue: route to /bookshelf/playlists on library change
- collection/_id.vue: route to /bookshelf/collections unless the new
  library is the collection's own library

pages/collection/_id.vue

@@ -135,8 +135,20 @@ export default {
           this.$eventBus.$emit('play-item', { libraryItemId: nextBookNotRead.id })
         }
       }
+    },
+    libraryChanged(libraryId) {
+      // A collection belongs to a single library, so leave this page when a different library is
+      // selected rather than showing a collection that is not in the current library
+      if (!libraryId || libraryId !== this.collection.libraryId) {
+        this.$router.replace('/bookshelf/collections')
+      }
     }
   },
-  mounted() {}
+  mounted() {
+    this.$eventBus.$on('library-changed', this.libraryChanged)
+  },
+  beforeDestroy() {
+    this.$eventBus.$off('library-changed', this.libraryChanged)
+  }
 }
 </script>

pages/playlist/_id.vue

@@ -162,13 +162,20 @@ export default {
       if (this.playlist.id === playlist.id) {
         this.$router.replace('/bookshelf/playlists')
       }
+    },
+    libraryChanged() {
+      // Playlist contents are shown in the context of the selected library, so leave this page
+      // when the library changes rather than showing stale items
+      this.$router.replace('/bookshelf/playlists')
     }
   },
   mounted() {
+    this.$eventBus.$on('library-changed', this.libraryChanged)
     this.$socket.$on('playlist_updated', this.playlistUpdated)
     this.$socket.$on('playlist_removed', this.playlistRemoved)
   },
   beforeDestroy() {
+    this.$eventBus.$off('library-changed', this.libraryChanged)
     this.$socket.$off('playlist_updated', this.playlistUpdated)
     this.$socket.$off('playlist_removed', this.playlistRemoved)
   }