Clean up after errors and fix related bugs:

It was freeing the wrong object when there was an error
attaching an object to its parent!

Don't crash when printing null (partially read) hash values.

jsonpull.h

@@ -33,6 +33,7 @@ typedef struct json_pull {
 	void *source;
 
 	json_object *container;
+	json_object *root;
 } json_pull;
 
 json_pull *json_begin_file(FILE *f);