{"action":"created","issue":{"url":"https://api.github.com/repos/chenglou/react-motion/issues/180","labels_url":"https://api.github.com/repos/chenglou/react-motion/issues/180/labels{/name}","comments_url":"https://api.github.com/repos/chenglou/react-motion/issues/180/comments","events_url":"https://api.github.com/repos/chenglou/react-motion/issues/180/events","html_url":"https://github.com/chenglou/react-motion/issues/180","id":109490355,"number":180,"title":"Uncaught TypeError: Cannot read property 'config' of undefined","user":{"login":"lencioni","id":195534,"avatar_url":"https://avatars.githubusercontent.com/u/195534?v=3","gravatar_id":"","url":"https://api.github.com/users/lencioni","html_url":"https://github.com/lencioni","followers_url":"https://api.github.com/users/lencioni/followers","following_url":"https://api.github.com/users/lencioni/following{/other_user}","gists_url":"https://api.github.com/users/lencioni/gists{/gist_id}","starred_url":"https://api.github.com/users/lencioni/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/lencioni/subscriptions","organizations_url":"https://api.github.com/users/lencioni/orgs","repos_url":"https://api.github.com/users/lencioni/repos","events_url":"https://api.github.com/users/lencioni/events{/privacy}","received_events_url":"https://api.github.com/users/lencioni/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":2,"created_at":"2015-10-02T13:25:22Z","updated_at":"2015-10-02T13:58:14Z","closed_at":null,"body":"I am upgrading from 0.2.7 to 0.3.0 and I ran into an error:\r\n\r\n> Uncaught TypeError: Cannot read property 'config' of undefined\r\n\r\nThis happens when I am using a `TransitionMotion` with a style object that has a key who's value is `undefined`, e.g.:\r\n\r\n```js\r\n{\r\n  opacity: spring(0),\r\n  extraText: undefined,\r\n}\r\n```\r\n\r\nThis is happening on https://github.com/chenglou/react-motion/blob/d478fe6ba1a5ba74ab364747f063e16fa8c3185f/src/updateTree.js#L38\r\n\r\nI can side-step the issue by setting that value to something other than `undefined` or `null`, but it would be nice if I didn't have to. I believe this could be avoided by adding a couple of checks here and there, for example:\r\n\r\n```js\r\nif (!style[key].config) {\r\n```\r\n\r\ncould be changed to\r\n\r\n```js\r\nif (!style[key] || !style[key].config) {\r\n```"},"comment":{"url":"https://api.github.com/repos/chenglou/react-motion/issues/comments/145029210","html_url":"https://github.com/chenglou/react-motion/issues/180#issuecomment-145029210","issue_url":"https://api.github.com/repos/chenglou/react-motion/issues/180","id":145029210,"user":{"login":"lencioni","id":195534,"avatar_url":"https://avatars.githubusercontent.com/u/195534?v=3","gravatar_id":"","url":"https://api.github.com/users/lencioni","html_url":"https://github.com/lencioni","followers_url":"https://api.github.com/users/lencioni/followers","following_url":"https://api.github.com/users/lencioni/following{/other_user}","gists_url":"https://api.github.com/users/lencioni/gists{/gist_id}","starred_url":"https://api.github.com/users/lencioni/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/lencioni/subscriptions","organizations_url":"https://api.github.com/users/lencioni/orgs","repos_url":"https://api.github.com/users/lencioni/repos","events_url":"https://api.github.com/users/lencioni/events{/privacy}","received_events_url":"https://api.github.com/users/lencioni/received_events","type":"User","site_admin":false},"created_at":"2015-10-02T13:58:14Z","updated_at":"2015-10-02T13:58:14Z","body":"Flow would be sweet. In the meantime, I'll submit a PR that addresses this issue."}}