Fix some build issues with C++, yay!

Author: zacharycmontoya

test/system-tests/request_handler.cpp

@@ -114,10 +114,16 @@ void RequestHandler::on_span_start(const httplib::Request& req,
       auto span = parent_span_it->second.create_child(span_cfg);
       success(span, res);
       active_spans_.emplace(span.id(), std::move(span));
-    } else if (parent_header_it == http_headers_.cend()) {
-      auto span = tracer_.extract_span(utils::HeaderReader(*parent_header_it), span_cfg);
-      success(span, res);
-      active_spans_.emplace(span.id(), std::move(span));
+    } else if (parent_header_it != http_headers_.cend()) {
+      auto span = tracer_.extract_span(utils::HeaderReader(parent_header_it->second), span_cfg);
+      if (span) {
+        success(*span, res);
+        active_spans_.emplace(span->id(), std::move(*span));
+      } else {
+        const auto msg = "on_span_start: unable to create span from http_headers identified by parent_id " +
+                          std::to_string(*parent_id);
+        VALIDATION_ERROR(res, msg);
+      }
     } else {
       const auto msg = "on_span_start: span or http_headers not found for id " +
                         std::to_string(*parent_id);
@@ -240,12 +246,14 @@ void RequestHandler::on_extract_headers(const httplib::Request& req,
     VALIDATION_ERROR(res, error->with_prefix("on_extract_headers: ").message);
   }
 
+// clang-format off
   const auto response_body = nlohmann::json{
-      {"span_id", span->parent_id()},
+      {"span_id", span->parent_id().value() },
   };
+// clang-format on
 
   res.set_content(response_body.dump(), "application/json");
-  http_headers_.emplace(span->parent_id(), std::move(*http_headers));
+  http_headers_.emplace(span->parent_id().value(), std::move(*http_headers));
 }
 
 void RequestHandler::on_span_flush(const httplib::Request& /* req */,