New protocol is added even though the operation is canceled

[DurieuxPol]

When you add a protocol with the "New protocol" menu, if you start typing the name of an existing protocol and you press the Cancel button, the protocol is added anyway while it shouldn't.
This is for Pharo 13.

For example:

• create a new class "MyClass", right click in the protocol column and select "New protocol"

• start typing the name of an existing protocol, like "sort". Notice that the first existing protocol is selected by default

• press the Cancel button. The protocol is added regardless

It might be related this method StProtocolNameChooserPresenter class>>#requestProtocolNameConfiguring: and to issue #17978

[Ducasse]

Tx Pol!

[jecisc]

Fix proposed here: pharo-spec/NewTools#1082