vue updated model before teardown component

[FQZhang]

Vue.js version

1.0.21

Reproduction Link

https://jsfiddle.net/72oozov2/15/

Steps to reproduce

1. Turn on "Set Background",
2. Turn on "Set Background Colour"
3. Turn off "Set Background"
4. Look at Browser DevTools

What is Expected?

No error displaying. app keeps on working

What is actually happening?

Got an error: [Vue warn]: Error when evaluating expression "styles.bg.colour": TypeError: Cannot read property 'colour' of undefined

The error stops app to keep on working

[zigomir]

@FQZhang You can solve it like so: https://jsfiddle.net/72oozov2/16/

I don't think this is Vue's problem per se, because in my opinion using Vue.set or Vue.delete inside watcher will always allow for such edge cases when error will appear.