Fix feature validation when feature doesn't exist

Description

Fix the exception caused by trying to access getKey() method on a null feature. This error occurs when you try to check a feature that does not exist in the subscription.

Error

Error occurs when you try to check a feature using canUseFeature() method. If the feature you try to check doesn't exist in the subscription, it gets this exception:

{
    "message": "Call to a member function getKey() on null",
    "exception": "Error",
    "file": "D:\\negocios\\touristock\\app\\vendor\\rinvex\\laravel-subscriptions\\src\\Models\\PlanSubscriptionUsage.php",
    "line": 138,
    "trace": [
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Eloquent\\Model.php",
            "line": 1467,
            "function": "scopeByFeatureSlug",
            "class": "Rinvex\\Subscriptions\\Models\\PlanSubscriptionUsage",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Eloquent\\Builder.php",
            "line": 1206,
            "function": "callNamedScope",
            "class": "Illuminate\\Database\\Eloquent\\Model",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Eloquent\\Builder.php",
            "line": 1187,
            "function": "Illuminate\\Database\\Eloquent\\{closure}",
            "class": "Illuminate\\Database\\Eloquent\\Builder",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Eloquent\\Builder.php",
            "line": 1205,
            "function": "callScope",
            "class": "Illuminate\\Database\\Eloquent\\Builder",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Eloquent\\Builder.php",
            "line": 1637,
            "function": "callNamedScope",
            "class": "Illuminate\\Database\\Eloquent\\Builder",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Support\\Traits\\ForwardsCalls.php",
            "line": 23,
            "function": "__call",
            "class": "Illuminate\\Database\\Eloquent\\Builder",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Support\\Traits\\ForwardsCalls.php",
            "line": 52,
            "function": "forwardCallTo",
            "class": "Illuminate\\Database\\Eloquent\\Relations\\Relation",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Eloquent\\Relations\\Relation.php",
            "line": 481,
            "function": "forwardDecoratedCallTo",
            "class": "Illuminate\\Database\\Eloquent\\Relations\\Relation",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\vendor\\rinvex\\laravel-subscriptions\\src\\Models\\PlanSubscription.php",
            "line": 503,
            "function": "__call",
            "class": "Illuminate\\Database\\Eloquent\\Relations\\Relation",
            "type": "->"
        },
        {
            "file": "D:\\negocios\\touristock\\app\\app\\Models\\User.php",
            "line": 143,
            "function": "canUseFeature",
            "class": "Rinvex\\Subscriptions\\Models\\PlanSubscription",
            "type": "->"
        },
        ...
    ]
}

The exception is caused by this line:

return $builder->where('feature_id', $feature->getKey() ?? null);

the problem is null coalescing operator ( ?? ) check if the previous variable is set or not null, trying to access a method on a null object(as in the code above) throw a exception that is not catch by the null coalescing operator.

Solutions

one posible solution is replace the null coalescing operator with a ternary operator:

return $builder->where('feature_id', $feature ? $feature->getKey() : null);

This works as expected returning null in case no feature is found.

rinvex / laravel-subscriptions