refactor(addRoute): create route only when parent.alias exists (#3569)

* fix(addRoute): create routing only when parent.alias exists

* refactor(addRoute): create route only when parent.alias is not an empty array

if parent.alias is an empty array, there is no need to execute createRouteMap

Co-authored-by: Eduardo San Martin Morote <posva@users.noreply.github.com>

Co-authored-by: wangqiang025 <wangqiang025@ke.com>
Co-authored-by: Eduardo San Martin Morote <posva@users.noreply.github.com>

src/create-matcher.js

@@ -32,7 +32,7 @@ export function createMatcher (
     createRouteMap([route || parentOrRoute], pathList, pathMap, nameMap, parent)
 
     // add aliases of parent
-    if (parent) {
+    if (parent && parent.alias.length) {
       createRouteMap(
         // $flow-disable-line route is defined if parent is
         parent.alias.map(alias => ({ path: alias, children: [route] })),