Check if easy response is null when returning a char *

Author: JosephP91

include/curl_easy_info.h

@@ -51,6 +51,9 @@ namespace curl {
     public:
         curl_easy_info(char *pointer) : _pointer(pointer) {}
         std::string get() const {
+            if (_pointer == nullptr) {
+                return std::string('');
+            }
             return std::string(_pointer);
         }
     private: