FIX: currentURL is unstable for in route transitions

If you transition just using query params but leave the rest of the route
alone, sometimes router.currentURL will not update.

This in turn causes active not to work correctly.

assets/javascripts/discourse-assign/initializers/extend-for-assigns.js.es6

@@ -69,10 +69,13 @@ function initialize(api) {
       }
     },
     forceActive: (category, args, router) => {
+      const queryParams = router.currentRoute.queryParams;
+
       return (
-        router.currentURL &&
-        router.currentURL.indexOf("assigned=nobody") > -1 &&
-        router.currentURL.indexOf("status=open") > -1
+        queryParams &&
+        Object.keys(queryParams).length === 2 &&
+        queryParams["assigned"] === "nobody" &&
+        queryParams["status"] === "open"
       );
     },
     before: "top"