Missing button in grand prix editor name dialog

Hello,
I am a Mathieu, a software engineering student in Montreal. It's my first time contributing in an open source project, I hope everything is okay. Here is the pull request regarding the issue #1765 that I recently opened regarding a very small UI improvement for the grand prix Editor name entering dialog. I  also refactored a part of the EnterGPNameDialog::onEnterPressedInternal() to a validateName() method. Don't worry, I plan to do bigger contributions in the near future. Have a great day, I'm going back to studying my exam hihihi !

EDIT : Instead of studying, I also gave a shot to issue #1762.