How fix Solution when have been added website from filesystem without project file

Conversion tool migration aborted.
When migrating a webforms solution it is possible to experience an error related to a project with an invalid empty extension.
Cannot convert projects with extension . Please remove the project with extension from the solution you want to convert and try it again.

When this error happened?

This happens when a website is added to a solution from a filesystem directory.
Step 1: Select add website
Add existing website
Step 2: Select the directory from filesystem
Select directory for website
Step 3: WebSite is added to solution
WebSite added

How to Fix?

Step 1: Remove the existing website from solution
Remove website
Step 2: Add new project (This will be used as a template for the existing website)
Add new project
Step 3: Select new Web Application
Select Web Application
Step 4: Configure the project with a different name of the existing folder with the website files in it.
Step 5: Create the WebForms project
Create the WebForms Application
Step 6: Rename the created project with original website name
Step 7: Remove the project from the solution.
Step 8: Copy the generated csproj file to the original website directory
Step 10: Add the existing project in the original website directory to the solution
Add the existing project
Step 11: Select option in solution explorer Show all Files
Show all files
Step 12: Include the files to the project and exclude the ones that are not going to be part
Step 13: Add the needed references to the project. (Can use as reference the ones in the solution file, that exist for the original website)
Solution File References
Step 14: Compile and try to migrate