Use array_key_exists instead of isset for "_findVariableInContext"

[ThePixelDeveloper]

A bit of information on this bug.

Say I have a class with a $description property, value being the meta description of a website.

Now I have a form method in a child view class that returns an array with form values. Like

public function form()
{
    $default = array
    (
        'name'        => NULL,
        'description' => NULL,
        'tags'        => NULL,
    );

    return array_intersect_key($this->form, $default);
}

The initial page load would set the description value to that of the meta description (even though the key is set). This is because isset returns false for an array key that has a NULL value. array_key_exists solves this problem nicely.

[bobthecow]

Thanks! Pulled into dev. This will go in 0.4 since it's a backwards incompatible change.