fix: useElementScriptTrigger support undefined trigger

Author: harlan-zw

src/runtime/composables/useElementScriptTrigger.ts

@@ -52,6 +52,8 @@ export function useElementScriptTrigger(options: ElementScriptTriggerOptions): P
     return new Promise<void>(() => {})
   if (el && options.trigger === 'visible')
     return useElementVisibilityPromise(el)
+  if (!trigger)
+    return Promise.resolve()
   if (trigger !== 'immediate') {
     // TODO optimize this, only have 1 instance of intersection observer, stop on find
     return new Promise<void>((resolve) => {