Fix serialization bug introduced in 9eddcfc42f

src/EventAccessors.cpp

@@ -404,5 +404,5 @@ mtx::accessors::media_width(const mtx::events::collections::TimelineEvents &even
 nlohmann::json
 mtx::accessors::serialize_event(const mtx::events::collections::TimelineEvents &event)
 {
-        return std::visit([](const auto &e) { return nlohmann::json{e}; }, event);
+        return std::visit([](const auto &e) { return nlohmann::json(e); }, event);
 }