Every time I open a Sublime Text 3 project, an empty window opens (“Untitled”) in addition to my project/workspace. How do I disable this? I’ve tried “create_window_at_startup”: false but that doesn’t work (I’m on Win 7 anyways, and it says that setting is only for OSX).
Sublime Text version: 3 build 3047 
I get a similar thing but not sure if exactly as you say. This happens when there is no ST window currently open, then i go right click a sublime-project file and click open with sublime text. What happens is that the last active project is loaded and on top of it a blank window is loaded with the actual project i wanted to open. It doesn’t seem to load the workspace, it forgets all the tabs I had open on that project. If you happen to do that with the same project as the last active one it loads it twice as you say, the second being a blank/empty window.
FYI, although it has been 11 year after, I’d like to leave this info to whoever is still searching for this answer. The feature “create_window_at_startup: false" will not work even if you put it into the “User/Preferences.sublime-settings” which was thought to override the “Default/Preferences.sublime-settings”, you have to put it into “Settings - Syntax Specific”. This has been tested on MacBook, you can try this on windows too.