add a safeguard against NULL return output stream

diff --git a/janssonxx.h b/janssonxx.h
index e09010d..57e2aed 100644 (file)
--- a/janssonxx.h
+++ b/janssonxx.h
@@ -265,8 +265,10 @@ private:
 // stream JSON value out
 std::ostream& operator<<(std::ostream& os, const jansson::Value& value) {
        char* tmp = value.save_string();
-       os << tmp;
-       free(tmp);
+       if (tmp != 0) {
+               os << tmp;
+               free(tmp);
+       }
        return os;
 }