Only show invite button when possible

lib/views/chat_details.dart

@@ -141,7 +141,8 @@ class _ChatDetailsState extends State<ChatDetails> {
                         ),
                       ],
                     ),
-                    ListTile(
+                    widget.room.canInvite
+                        ? ListTile(
                             title: Text("Invite contact"),
                             leading: Icon(Icons.add),
                             onTap: () => Navigator.of(context).push(
@@ -150,7 +151,8 @@ class _ChatDetailsState extends State<ChatDetails> {
                                 InvitationSelection(widget.room),
                               ),
                             ),
-                    ),
+                          )
+                        : Container(),
                   ],
                 )
               : i < members.length + 1