Steps to reproduce:
1. Unzip the attached project "TestCreate"
2. Locate the TestCreate.CSharp.csproj file in the project folder and open it with Visual Studio
3. In the Solution Explorer expand the 'References' bar and notice that the 'Analyzers' bar has several attributes
4. Go to the 'Assets' folder in the Unity project and create a 'test.txt' file
5. Open the project in Unity and notice that the file 'test' has been imported
6. Go back to the project folder and reopen the TestCreate.CSharp.csproj file
7. In the Solution Explorer expand the 'References' bar and notice that the 'Analyzers' no longer has any attributes

Expected: the 'Analyzers' bar has several attributes
Actual: .csproj file is missing 'Analyzer' packages after Assets are loaded

Reproduced: 5.2.4f1, 5.3.4p3, 5.4.0b14