Summary

Fixes #1157

Adds a nil check for rootViewController before adding the control view to the window in updateViewHierarchy.

Problem

When SVProgressHUD is shown, it adds its control view to the front window. If the window exists but has no rootViewController (or it's in an invalid state during app transitions), UIKit throws an NSInternalInconsistencyException when resolving trait collection for the new subview.

Solution

Check that window.rootViewController is not nil before adding the subview:

UIWindow *window = self.frontWindow;
if (window.rootViewController) {
    [window addSubview:self.controlView];
}

Testing

• Verified the fix compiles correctly
• If no valid window is available, the HUD simply won't be shown (graceful degradation)