Pass an empty object to scoped slots (#1660)

Match how the Vue runtime executes scoped slots. When a scoped slot
accepts and immediately destructures its props, an error will get thrown
if attempting to destructure a value that is `undefined`.

Author: sirlancelot

Diff for: packages/create-instance/create-component-stubs.js

@@ -150,7 +150,7 @@ export function createStubFromComponent(
           ? context.children
           : this.$options._renderChildren ||
               getScopedSlotRenderFunctions(this).map(x =>
-                this.$options.parent._vnode.data.scopedSlots[x]()
+                this.$options.parent._vnode.data.scopedSlots[x]({})
               )
       )
     }