Don't open file chooser on "Open Project" view
How to reproduce:
- open Builder
- open a project
- choose "Open Project" from the app menu
- a new window opens with the project list, but on top of that a file chooser is also opened
This behavior is annoying when you want to access a project that's already in the project list (which is what I personally do most of the time). If quick access to projects that aren't in Builder yet is a goal, we could add something like "Add Project" as a new menu entry, which would open a file chooser.