Add a cast from json to std::string for the anchor in the Horizonsdialog(#3548)

This fixes compilation with GCC 14.2.1

apps/OpenSpace/ext/launcher/src/profile/horizonsdialog.cpp

@@ -858,7 +858,7 @@ openspace::HorizonsFile HorizonsDialog::handleAnswer(nlohmann::json& answer) {
 
     auto it = answer.find("error");
     if (it != answer.end()) {
-        _latestHorizonsError = *it;
+        _latestHorizonsError = it->get<std::string>();
     }
 
     HorizonsResultCode isValid = isValidHorizonsAnswer(answer);

src/navigation/navigationstate.cpp

@@ -114,7 +114,7 @@ NavigationState::NavigationState(const nlohmann::json& json) {
     position.y = json["position"]["y"].get<double>();
     position.z = json["position"]["z"].get<double>();
 
-    anchor = json["anchor"];
+    anchor = json["anchor"].get<std::string>();
 
     if (auto it = json.find("referenceframe");  it != json.end()) {
         referenceFrame = it->get<std::string>();