Android app crashes after permission set: Ionic capacitor

Here i have simple ionic app followed by this tutorial , and it works well, but when i run the android application for the first time and once i trying to access FileSystem or Camera functionalities, app asks for the permission and once i gave the permission application crashes with Unfortunately, app has stopped. message. And after that it works fine.

Updated

It happened with Android API level 23, and once i tried with API level 27 and 29 it works fine.

variables.gradle

ext {
    minSdkVersion = 21
    compileSdkVersion = 29
    targetSdkVersion = 29
    ...
 }

And i' using latest versions of both Ionic and Capacitor.

Whats happening here ?