Fixed race condition when you hide with delay and in the meantime you show the HUD again

Hey!

A simple fix in order to solve this problem I'm having in my projects.

The use of [NSRunLoop cancelPreviousPerformRequestsWithTarget:self] is convenient since there's only one call to [self performSelector:...] but when more performSelector calls appear, it has to be changed to the other version of the method (passing both target, selector and argument)

Let me know if you have any question

Thanks!