fix(vuex): make sure flushStoreModules return array (#954)
fix(vuex): make sure flushStoreModules return array (#954)

When the vuex store does not have `registerModule`, `flushStoreModules` will return `undefined` and make the following calls on hook.storeModules failed.

This happened in my early version of vuex apps.


vuejs/vue-devtools,vuejs/vue-devtools