Handle cases where Wizard Step is not found (hidden steps)

[AlexisSerneels]

Description

Found related issue : #4916 (comment)

I encountered the same exception in my project:

Undefined array key -1 at /vendor/filament/forms/src/Components/Wizard.php:78

It happens because the method findIndex(...)returns -1 if no item is found.
Thus the getStepIndex()returns -1 which does not exists and throws a 500 Exception.

This PR fixes this issue by returning the first Wizard step instead.

Visual changes

None

Functional changes

• Code style has been fixed by running the composer cs command.
• Changes have been tested to not break existing functionality.
• Documentation is up-to-date.

[danharrin]

To be honest, it doesn't feel like you've tested this. index = this.getSteps()[0] assigns the ID of the step instead of its index doesn't it? Doesn't it just need to be index = 0?

[AlexisSerneels]

Sorry about the wrong copy/paste into Github Issue PR. You are correct.
Thank you for the strict comparison operator correction.