[skip changelog] use absolute URL in docs version selector (#718)

Author: Massimiliano Pippi

docs/js/version-select.js

@@ -35,7 +35,7 @@ window.addEventListener("DOMContentLoaded", function () {
       return { text: i.title, value: i.version };
     }), realVersion);
     select.addEventListener("change", function (event) {
-      window.location.href = REL_BASE_URL + "/../" + this.value;
+      window.location.href = ABS_BASE_URL + "/../" + this.value;
     });
 
     var container = document.createElement("div");