fix: call onNavigatingFrom event only if it exists (#6773)

grgur · manoldonev · commit 19dfd163e090 · 2019-01-21T15:23:43.000+02:00
I ran into an issue where `owner.onNavigatingFrom` didn't exist when rendering a view was blocked by the biometric scanner and then user hit the back button to navigate back.

This code simply adds a check to see if `onNavigatingFrom` exists on the owner
diff --git a/tns-core-modules/ui/page/page.ios.ts b/tns-core-modules/ui/page/page.ios.ts
@@ -177,7 +177,7 @@ class UIViewControllerImpl extends UIViewController {
         // or because we are closing a modal page, 
         // or because we are in tab and another controller is selected.
         const tab = this.tabBarController;
-        if (!owner._presentedViewController && !this.presentingViewController && frame && frame.currentPage === owner) {
+        if (owner.onNavigatingFrom && !owner._presentedViewController && !this.presentingViewController && frame && frame.currentPage === owner) {
             const willSelectViewController = tab && (<any>tab)._willSelectViewController;
             if (!willSelectViewController
                 || willSelectViewController === tab.selectedViewController) {
