add owner check

Author: PeterStaev

src/bottom-navigation/index.ios.ts

@@ -51,9 +51,12 @@ class UITabBarControllerImpl extends UITabBarController {
     // @profile
     public viewDidDisappear(animated: boolean): void {
         super.viewDidDisappear(animated);
-        const owner = this._owner.get();
-        if (owner && !owner.parent && owner.isLoaded && !this.presentedViewController) {
-            owner.callUnloaded();
+
+        if (this._owner) {
+            const owner = this._owner.get();
+            if (owner && !owner.parent && owner.isLoaded && !this.presentedViewController) {
+                owner.callUnloaded();
+            }
         }
     }