Tests moved into separate folders (#3794)

Fix android crash on application exit

tns-core-modules/ui/core/view-base/view-base.ts

@@ -634,6 +634,11 @@ export class ViewBase extends Observable implements ViewBaseDefinition {
     }
 
     public _tearDownUI(force?: boolean) {
+        // No context means we are already teared down.
+        if (!this._context) {
+            return;
+        }
+
         if (traceEnabled()) {
             traceWrite(`${this}._tearDownUI(${force})`, traceCategories.VisualTreeEvents);
         }