System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindCollectionMapping(RelationalTypeMappingInfo info, Type modelType, Type providerType, CoreTypeMapping elementMapping)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerTypeMappingSource.FindCollectionMapping(RelationalTypeMappingInfo info, Type modelType, Type providerType, CoreTypeMapping elementMapping)
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.<>c.<FindMappingWithConversion>b__8_0(ValueTuple`4 k, RelationalTypeMappingSource self)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd[TArg](TKey key, Func`3 valueFactory, TArg factoryArgument)
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindMappingWithConversion(RelationalTypeMappingInfo mappingInfo, Type providerClrType, ValueConverter customConverter)
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindMappingWithConversion(RelationalTypeMappingInfo mappingInfo, IReadOnlyList`1 principals)
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindMapping(IProperty property)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.<>c.<get_TypeMapping>b__96_0(IProperty property)
   at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.get_TypeMapping()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IReadOnlyProperty.FindTypeMapping()
   at Microsoft.EntityFrameworkCore.RelationalPropertyExtensions.FindRelationalTypeMapping(IReadOnlyProperty property)
   at Microsoft.EntityFrameworkCore.RelationalPropertyExtensions.GetColumnType(IReadOnlyProperty property)
   at Microsoft.EntityFrameworkCore.RelationalPropertyExtensions.GetColumnType(IProperty property)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.RelationalModel.CreateDefaultColumnMapping(ITypeBase typeBase, ITypeBase mappedType, TableBase defaultTable, TableMappingBase`1 tableMapping, Boolean isTph, Boolean isTpc, IRelationalTypeMappingSource relationalTypeMappingSource)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.RelationalModel.AddDefaultMappings(RelationalModel databaseModel, IEntityType entityType, IRelationalTypeMappingSource relationalTypeMappingSource)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.RelationalModel.Create(IModel model, IRelationalAnnotationProvider relationalAnnotationProvider, IRelationalTypeMappingSource relationalTypeMappingSource, Boolean designTime)
   at Microsoft.EntityFrameworkCore.Infrastructure.RelationalModelRuntimeInitializer.<>c__DisplayClass4_0.<InitializeModel>b__0()
   at Microsoft.EntityFrameworkCore.RelationalModelExtensions.<>c.<GetRelationalModel>b__4_0(Func`1 f)
   at Microsoft.EntityFrameworkCore.Infrastructure.AnnotatableBase.<>c__30`2.<GetOrAddRuntimeAnnotationValue>b__30_0(String n, ValueTuple`3 t)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd[TArg](TKey key, Func`3 valueFactory, TArg factoryArgument)
   at Microsoft.EntityFrameworkCore.Infrastructure.AnnotatableBase.GetOrAddRuntimeAnnotationValue[TValue,TArg](String name, Func`2 valueFactory, TArg factoryArgument)
   at Microsoft.EntityFrameworkCore.RelationalModelExtensions.GetRelationalModel(IModel model)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language, Boolean dryRun)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace, Boolean dryRun)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace, Boolean dryRun)
   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)