fix: Add fallback values to Composition API methods

Author: mvsde

lib/use.js

@@ -13,21 +13,21 @@ import { getCurrentInstance } from 'vue'
  */
 export function useData () {
 	const app = getCurrentInstance()
-	return app.appContext.config.globalProperties.$data
+	return app?.appContext.config.globalProperties.$data ?? {}
 }
 
 /**
  * @returns {Object<string,function>}
  */
 export function useMethods () {
 	const app = getCurrentInstance()
-	return app.appContext.config.globalProperties.$methods
+	return app?.appContext.config.globalProperties.$methods ?? {}
 }
 
 /**
- * @returns {string}
+ * @returns {string|null}
  */
 export function useCSS () {
 	const app = getCurrentInstance()
-	return app.appContext.config.globalProperties.$css
+	return app?.appContext.config.globalProperties.$css
 }