Uninitiated current_loop_data bug fix in render_to (#165)

* uninitiated current_loop_data bug fix in render_to

* change json_loop_data to  json_additional_data

* forgot to update single_include
diff --git a/include/inja/renderer.hpp b/include/inja/renderer.hpp
index cb9ac0f..688a912 100644
--- a/include/inja/renderer.hpp
+++ b/include/inja/renderer.hpp
@@ -593,6 +593,7 @@
     json_input = &data;
     if (loop_data) {
       json_additional_data = *loop_data;
+      current_loop_data = &json_additional_data["loop"];
     }
 
     current_template->root.accept(*this);
diff --git a/single_include/inja/inja.hpp b/single_include/inja/inja.hpp
index 0a35699..0d32120 100644
--- a/single_include/inja/inja.hpp
+++ b/single_include/inja/inja.hpp
@@ -3888,6 +3888,7 @@
     json_input = &data;
     if (loop_data) {
       json_additional_data = *loop_data;
+      current_loop_data = &json_additional_data["loop"];
     }
 
     current_template->root.accept(*this);