fix: on destroy remove the lastBootstrappedModule

If exit event was triggered twice we would try to destroy an already
destroy module ref.

Author: m-abs

nativescript-angular/platform-common.ts

@@ -260,6 +260,8 @@ export class NativeScriptPlatformRef extends PlatformRef {
             "nativescript-angular/platform-common.exitCallback", () => {
                 const lastModuleRef = lastBootstrappedModule ? lastBootstrappedModule.get() : null;
                 if (lastModuleRef) {
+                    lastBootstrappedModule = null;
+
                     lastModuleRef.destroy();
                 }