The error happens because the QualitySettings.asset file (inside the ProjectSettings/ folder) has been renamed to be "ProjectSettings.asset".
The ProjectSettings.asset asset should contain a "PlayerSettings" object and not a "QualitySettings" object. As such, when the system tries to load up the file, it fails.
Deleting the "ProjectSettings/ProjectSettings.asset" file will force Unity to create a new one. Alternatively, copying an existing one from another project (assuming it doesn't have the same issue) should also fix the particular issue.