Setting indeterminate property when progress view has no window has no effect

[toddreed]

The value of the indeterminate property is based on the presence of the spin animation on the view's layer. This causes an issue when attempting to set the indeterminate property to YES when the view doesn't belong to a window because the animation is not preserved when the view is moved to a window; iOS seems to remove all animations when a view is added to a window.

[Vyazovoy]

@danielamitay Daniel, it is very desirable PR. I spent all day to figure out this bug :)) Merge this ASAP, please. Thank you @toddreed