observer leak bug fix

[bestwnh]

fix a observer leak if the developer set the show status to YES before
add the handler.

[bestwnh]

I also create an issue about this bug. #222

[martsen]

Thanks! It really helped me.

[dennisreimann]

Can this be brought in? It otherwise crashes a lot of times for me when moving away from a controller that has pull to refresh and/or infinite scrolling enabled...

[bestwnh]

@dennisreimann I don't understand. Could you provide more information or some sample code?

[dennisreimann]

@bestwnh All is fine, I just wanted to reassure that this is also happening for me in case your fix is not present. So please, merge this into the official version!

[bestwnh]

@dennisreimann I really want to merge and already pull a request long time ago(Oct of 2014). But I don't receive any response. And I contact @samvermette and here is his response:

Hey Galvin,

Indeed I've long decided to give up on some of my classes, including SVPullToRefresh. It's especially true for that class since I've never actually used it in a production app. 

There are over 570 forks of SVPullToRefresh out there, I suggest you find the best and most actively maintained and put your hopes in that one :)

Sam

[dennisreimann]

Well, that's sad.

[bestwnh]

Yes. But he is still making some other amazing projects. So nothing to blame.
But it could be better if he can transfer this project to someone to continue.

[LawrenceHan]

Created a pull request in https://github.com/LawrenceHan/SVPullToRefresh
I will merge it after discusses with you.

[bestwnh]

@LawrenceHan Do whatever you want 😃

[LawrenceHan]

@bestwnh 昨天花了几个小时初步整理了一下pull request，fork到我的repo里了。
但是在合并进repo之前，我想先确认一下这个pull request是做什么，解决了什么问题，做过测试嘛。以防止引发其他问题。

所以能先说明一下，你的这个pull request解决了什么问题？

[bestwnh]

Oh, 同胞哦。问题说明在这上面有连接 #222 ，测试基本试过，其他人也用着没反馈新问题，其实就是加了个预判，不会引入什么新问题，你看看issue那边的说明然后看看相关代码就明白的了。

[LawrenceHan]

@bestwnh 已经合并了。