Return nullopt for state events in rooms we are not in

src/Cache_p.h

@@ -451,6 +451,7 @@ private:
                                                             const std::string &room_id,
                                                             std::string_view state_key = "")
     {
+        try {
             constexpr auto type = mtx::events::state_content_to_type<T>;
             static_assert(type != mtx::events::EventType::Unsupported,
                           "Not a supported type in state events.");
@@ -484,7 +485,6 @@ private:
                 }
             }
 
-        try {
             return json::parse(value).get<mtx::events::StateEvent<T>>();
         } catch (std::exception &e) {
             return std::nullopt;