fixes #481

[bilogic]

fixes #481 prevent exception by indicating that user() can be null

[what-the-diff]

PR Summary

• Improved Safety in 'canAccess' Method
  The canAccess method within our HasPageShield code has been updated to more effectively handle scenarios when the user is undefined or null. This prevents possible system errors or mishandling.

• Updated 'canView' Method for Better Null Handling
  The canView method in the HasWidgetShield portion of our code has also been updated. It now uses a technique known as the null-safe operator, which makes our application more resilient in cases where the user might not be defined or null.

[bezhanSalleh]

If you’re using Shield’s traits for guest pages and the panel, keep this in mind:

Shield provides traits to kickstart handling common scenarios. But, handling every unique use case isn’t its job—it’s near impossible.

To customize for your project, create traits specific to your needs and apply them to guest pages/widgets.

[bilogic]

I'm not using it for any guest pages

[bilogic]

@bezhanSalleh

1. https://github.com/illuminate/contracts/blob/4ce27a82391dd3050e85fe38ae50bc61dd8ece46/Auth/Guard.php#L21-L26
   • user() can return Authenticatable or null
2. The traits assume user() will always be Authenticatable and throws exceptions when null is returned
3. The traits break when the panels use ->login(null)
4. Please kindly accept this PR so that using ->login(null) won't cause exceptions

Thank you.