[NamespacedAttributeBag][HttpFoundation] Fixed bug to remove nonexistent element

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | --
| License       | MIT
| Doc PR        | --

Fixed a bug in NamespacedAttributeBag causing a Warning exception
by array_key_exists while try to remove noneexistent namespaced element.
The array_key_exists got a null in $attributes argument instead
empty array.

* Updated Syntax of remove method
* Added test for check remove unexistent element