The Entity Framework tools version '3.1.3' is older than that of the runtime '5.0.2'. Update the tools for the latest features and bug fixes. System.NullReferenceException: Object reference not set to an instance of an object. code example
Example: The EF Core tools version '3.1.0' is older than that of the runtime '3.1.3'
Use command line, Cmd or PowerShell for specific version:
dotnet tool update --global dotnet-ef --version 3.1.0
or
dotnet tool update --global dotnet-ef