step to reproduce:

1) create an empty solution using visual studio
"New Project">"Other Project Types">"Visual Studio Solution"

2) create a Qt project
"add">"New Project">"Qt Application"

3) create a new solution folder
"Add"->"New Solution Folder"

4) move this project to this folder

5) right click the project and click menu item "Qt Project Settings", a dialog appear which says "No Project Opened"