Error handling for no source record found

src/build.cpp

@@ -157,6 +157,7 @@ void build::set_lp(launchpad* lp_ptr) {
 }
 
 const std::optional<source_package_publishing_history> build::getCurrentSourcePublication() {
+    if (current_source_publication_link.empty()) return std::nullopt;
     auto response = lp->api_get(current_source_publication_link);
     if (!response) return std::nullopt;
     auto data = nlohmann::json::parse(response.value());