* RESTCONF in Clixon used empty key as "wildchar". But according to RFC 8040 it should mean the "empty string".

* Example: `GET restconf/data/x:a=`
  * Previous meaning (wrong): Return all `a` elements.
  * New meaning (correct): Return the `a` instance with empty key string: "".
* [RESTCONF GET request of single-key list with empty string returns all elements #213](https://github.com/clicon/clixon/issues/213)
* [RESTCONF GETof lists with empty string keys does not work #214](https://github.com/clicon/clixon/issues/214)

lib/src/clixon_path.c

@@ -713,7 +713,7 @@ api_path2xpath_cvv(cvec       *api_path,
 		goto done;
 	}
 	/* Check if has value, means '=' */
-        if (cv2str(cv, NULL, 0) > 0){
+	if (cv_type_get(cv) == CGV_STRING){
 	    /* val is uri percent encoded, eg x%2Cy,z */
             if ((val = cv2str_dup(cv)) == NULL)
                 goto done;