Add an empty view when a tagged user isnt found

Changelog-Added: Show a custom view when tagged user isn't found

damus/Views/Posting/UserSearch.swift

@@ -74,11 +74,16 @@ struct UserSearch: View {
     var body: some View {
         ScrollView {
             LazyVStack {
-                ForEach(users) { user in
-                    UserView(damus_state: damus_state, pubkey: user.pubkey)
-                        .onTapGesture {
-                            on_user_tapped(user: user)
-                        }
+                Divider()
+                if users.count == 0 {
+                    EmptyUserSearchView()
+                } else {
+                    ForEach(users) { user in
+                        UserView(damus_state: damus_state, pubkey: user.pubkey)
+                            .onTapGesture {
+                                on_user_tapped(user: user)
+                            }
+                    }
                 }
             }
         }