Check for set usb_device in iphone_free_device to avoid libusb segfault
Check for set usb_device in iphone_free_device to avoid libusb segfault

Signed-off-by: Matt Colyer <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@colyer.name>

upbit/libimobiledevice,patweb/libimobiledevice,upbit/libimobiledevice,kalev/libimobiledevice,Tatsh/libimobiledevice,Tatsh/libimobiledevice,upbit/libimobiledevice,kalev/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice,patweb/libimobiledevice,Tatsh/libimobiledevice,Tatsh/libimobiledevice,libimobiledevice/libimobiledevice,libimobiledevice-win32/libimobiledevice,patweb/libimobiledevice,libimobiledevice/libimobiledevice,kalev/libimobiledevice