Merge branch 'dev' of https://github.com/dcloudio/uni-app into v3

# Conflicts:
#	src/platforms/app-plus/service/api/index.js

src/core/service/plugins/util.js

 function callHook (vm, hook, params) {
-  return (vm.$vm || vm).__call_hook(hook, params)
+  vm = vm.$vm || vm
+  return vm.__call_hook && vm.__call_hook(hook, params)
 }
 
 export function callAppHook (vm, hook, params) {
   if (hook !== 'onError') {
     console.debug(`App：${hook} have been invoked` + (params ? ` ${JSON.stringify(params)}` : ''))
   }
-  return (vm.$vm || vm).__call_hook(hook, params)
+  vm = vm.$vm || vm
+  return vm.__call_hook && vm.__call_hook(hook, params)
 }
-
 export function callPageHook (vm, hook, params) {
   // hack 一下，H5 平台通知 View 层onShow，方便 View 层来切换 scroll 事件监听
   if (__PLATFORM__ === 'h5') {

src/platforms/app-plus/service/api/index.js

+export * from './base/event-bus'
 export * from './context/audio'
 export * from './context/background-audio'
 export * from './context/canvas'