fix crash

[daijianshusheng]

Today, I modify a file:

Filename:YPDocument.m

fixed Object is nil.

[mipmip]

Sounds great! Do you know how to create a pull request?

[daijianshusheng]

Don't know how to use the command line, get a while did not succeed, click "button to submit.
This should be submitted to the branch up? The first time I used, don't laugh at me.

[mipmip]

No worries. You must begin somewhere. You don't need the command line. Download the github client for the Mac

1. fork this repo
2. clone your own forked repo and make a change
3. commit and push your change. (please one at a time)
4. open your forked repo in your browser
5. create pull request

Good luck :)

[daijianshusheng]

Thank you. I've already configured it. Very convenient operation of the client software. I used it to submit changes later.