Magnet Links not working sometimes - bugfix

Found the bug that was causing some magnet link to not open.
Url escaping should be done as:
``` objc
[NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]
```
instead of
``` objc 
[url stringByReplacingOccurencesOfString:@" " withString:@"%20"]
```