Add try catch block to secure storage read

[pedroafmonteiro]

[BalloonWinter53]

As explained in the last meeting, not all the exceptions thrown by the flutter_secure_storage package are handled by it. In another implementation by Microsoft on their multi-platform framework's SecureStorage solution, they are very clear on the developer's role in handling exceptions.

With this in mind, a user (me) reported a bug where the app appears to freeze in the splash screen, due to it being stuck in this exception.