Try defining distro_series_link earlier

src/source_package_publishing_history.cpp

@@ -24,6 +24,7 @@ source_package_publishing_history::source_package_publishing_history()
     : source_package_name(""),
       source_package_version(""),
       self_link(""),
+      distro_series_link(""),
       lp(nullptr),
       distro_series([this]() -> std::optional<class distro_series> {
           if (distro_series_link.empty()) return std::nullopt;