Update FDTakeController.m

This fixes this crash for me:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Sheet can not be presented because the view is not in a window: <SWRevealView: 0x15533840; frame = (0 0; 320 568); autoresize = W+H; layer = <CALayer: 0x155247c0>>'
*** First throw call stack:
(0x307dee83 0x3ab3b6c7 0x331493d3 0x331b0a51 0x163fd5 0x16125f 0xd9c35 0xfd667 0x32e58893 0x330e9ea3 0x32f97355 0x32f92451 0x32f67d79 0x32f66569 0x307a9f1f 0x307a93e7 0x307a7bd7 0x30712471 0x30712253 0x3544c2eb 0x32fc7845 0x14a129 0x3b034ab7)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

http://stackoverflow.com/questions/18932544/nsinvalidargumentexception-reason-sheet-can-not-be-presented-because-the-vi