NullReferenceException when deleting optional fields

[Mrjuanblack]

Describe the bug Hello, I'm getting a NullReferenceException each time I try to create a migration where I delete any optional field from any defined entity.

To Reproduce

1. Have the following entity:

   [<CLIMutable>]
   type Dossier = {
   [<Key>]
   [<DatabaseGenerated(DatabaseGeneratedOption.Identity)>]
   Id : int
   TypeOfDossier : TypeOfDossier.TypeOfDossier
   InspectionLocation : InspectionLocation.InspectionLocation
   ...
   // Address
   Street : string
   Number : string
   Bus : string option
   PostalCode : string
   City : string
   ...
   OrderConfirmation : string option
   AssigmentConfirmation : string option
   Certificate : string option
   Lab : string option
   
   OrderConfirmationPhysicallySigned : string option
   AssignmentConfirmationPhysicallySigned : string option
   
   ManualInvoice: bool
   }  

2. Remove OrderConfirmationPhysicallySigned and/or AssignmentConfirmationPhysicallySigned (or any other optional field, I've tried with other optional text fields in other entities too)
3. Create a new migration

4. Get the following error:

   System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Initialize(ColumnOperation columnOperation, IColumn column, RelationalTypeMapping typeMapping, Boolean isNullable, IEnumerable`1 migrationsAnnotations, Boolean inline)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Add(IColumn target, DiffContext diffContext, Boolean inline)+MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.DiffCollection[T](IEnumerable`1 sources, IEnumerable`1 targets, DiffContext diffContext, Func`4 diff, Func`3 add, Func`3 remove, Func`4[] predicates)+MoveNext()
   
   at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Diff(ITable source, ITable target, DiffContext diffContext)+MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.DiffCollection[T](IEnumerable`1 sources, IEnumerable`1 targets, DiffContext diffContext, Func`4 diff, Func`3 add, Func`3 remove, Func`4[] predicates)+MoveNext()
   
   at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Sort(IEnumerable`1 operations, DiffContext diffContext)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetDifferences(IRelationalModel source, IRelationalModel target)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
   Object reference not set to an instance of an object.

Expected behavior A new migration without the deleted fields

Additional context We are using PostgreSQL as our db