What can I do to prevent the application from crashing when it is started again after the user denies the permission requested?

Possible Causes

If the permission required by a service is rejected by the user, the system directly returns the result.
If you do not verify the permission, the application may crash due to lack of permission.

Solution

Before allowing an application to call an API protected by certain permission, verify whether the application has the permission. If the application has the permission, the application can call the API. Otherwise, a dialog box is displayed to request user authorization.
If the user rejects to authorize a permission, ensure that the user can still use other features and can register and access the application.
When this service is triggered again by the user or to implement a service function, on-screen message shall be provided to guide the user to grant the permission in Settings.

Reference

Access Control Overview