fix: fix checking Reflect existance (#284)

Author: ktsn

src/component.ts

@@ -82,7 +82,7 @@ export function componentFactory (
 
   forwardStaticMembers(Extended, Component, Super)
 
-  if (reflectionIsSupported()) {
+  if (reflectionIsSupported) {
     copyReflectionMetadata(Extended, Component)
   }
 

src/reflect.ts

@@ -1,9 +1,7 @@
 import Vue, { VueConstructor } from 'vue'
 import { VueClass } from './declarations'
 
-export function reflectionIsSupported () {
-  return (Reflect && Reflect.defineMetadata) !== undefined
-}
+export const reflectionIsSupported = typeof Reflect !== undefined && Reflect.defineMetadata
 
 export function copyReflectionMetadata (
   to: VueConstructor,