Address code review feedback on remote_config desktop implementation

Author: AustinBenoit

remote_config/src/desktop/file_manager.cc

@@ -36,8 +36,9 @@ namespace internal {
 
 RemoteConfigFileManager::RemoteConfigFileManager(const std::string& filename,
                                                  const firebase::App& app) {
+  const char* package_name = app.options().package_name();
   std::string app_data_prefix =
-      std::string(app.options().package_name()) + "/remote_config";
+      std::string(package_name ? package_name : "") + "/remote_config";
   std::string error;
   std::string app_dir =
       AppDataDir(app_data_prefix.c_str(), /*should_create=*/true, &error);

remote_config/src/desktop/metadata.cc

@@ -85,8 +85,9 @@ void RemoteConfigMetadata::Deserialize(const std::string& buffer) {
     const char* key_str = settings.Keys()[i].AsKey();
     if (!key_str) continue;
     char* endptr = nullptr;
+    errno = 0;
     long raw_key = std::strtol(key_str, &endptr, 10);
-    if (endptr == key_str || *endptr != '\0') {
+    if (endptr == key_str || *endptr != '\0' || errno == ERANGE) {
       continue;
     }
     if (raw_key < std::numeric_limits<int>::min() ||