fix: Prevent success callback when ShareRequest fails to load.

[Roongf]

Previously, a success callback was incorrectly triggered when the ShareRequest encountered an issue and failed to load. This commit fixes the logic to ensure that the success callback is only invoked upon a successful ShareRequest.

This PR addresses an issue where the success callback of the Share API was being triggered even when the ShareRequest failed to load. This was incorrect behavior and led to misleading feedback to the user.

The change involves modifying the ShareApi class to correctly handle the loading state of the ShareRequest. Now, the success callback is only invoked when the ShareRequest has successfully loaded and the sharing process can proceed. If the request fails to load for any reason, an appropriate error or failure state is handled instead.

To test this change:

1. Ensure you have a scenario where the ShareRequest is likely to fail (e.g., missing parameters, network issues, or simulating a failure condition).
2. Initiate a share operation.
3. Verify that the success callback is not triggered and that the failure handling (if implemented) is correctly executed.

This change should not have any significant side effects, but it improves the robustness and reliability of the Share API's callback mechanism.

[CLAassistant]

All committers have signed the CLA.