Invalidating KVO on dismiss.

PullToDismissTransition.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = "PullToDismissTransition"
-  s.version          = "0.7.2"
+  s.version          = "0.7.3"
   s.homepage         = "https://github.com/benguild/PullToDismissTransition"
   s.summary          = "(Beta) Uses `UIPercentDrivenInteractiveTransition` and `UIViewControllerAnimatedTransitioning` to quickly implement nice “pull-to-dismiss” interactions on modal view controller(s). — Also handles `UIScrollView` bounce toggling dynamically when necessary. "
   s.license          = 'MIT'

PullToDismissTransition.swift

@@ -229,10 +229,13 @@ public class PullToDismissTransition: UIPercentDrivenInteractiveTransition {
                 }
 
                 viewController.dismiss(animated: true) { [weak self] in
-                    self?.delegate?.didFinishTransition(
-                        for: viewController,
-                        didDismiss: (viewController.presentingViewController == nil)
-                    )
+                    let didDismiss = (viewController.presentingViewController == nil)
+
+                    if didDismiss {
+                        self?.transitionDelegateObservation?.invalidate()
+                    }
+
+                    self?.delegate?.didFinishTransition(for: viewController, didDismiss: didDismiss)
                 }
 
                 delegate?.didBeginPullToDismissAttempt(on: viewController)