MSpec remover fails when MSpec context contains nested class with a reference to another nested class

[agross]

public class Something
{
  It does_not_matter;

  class Parent
  {
    public Child Child { get; set; }
  }

  class Child
  {
  }
}

When running Fody we receive the following NullReferenceException:

MSBUILD : error : Fody: An unhandled exception occurred:\r [d:\somewhere\some.csproj]
MSBUILD : error : Exception:\r [d:\somewhere\some.csproj]
MSBUILD : error : Object reference not set to an instance of an object.\r [d:\somewhere\some.csproj]
MSBUILD : error : StackTrace:\r [d:\somewhere\some.csproj]
MSBUILD : error :    at MSpecRemover.IsMspecField(FieldDefinition fieldDefinition) at c:\TeamCity\buildAgent\work\65b82fbfffdc864f\Fody\Removers\MSpecRemover.cs:line 39.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)\r [d:\somewhere\some.csproj]
MSBUILD : error :    at MSpecRemover.ContainsMSpecField(TypeDefinition typeDefinition) at c:\TeamCity\buildAgent\work\65b82fbfffdc864f\Fody\Removers\MSpecRemover.cs:line 34.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at MSpecRemover.ShouldRemoveType(TypeDefinition typeDefinition) at c:\TeamCity\buildAgent\work\65b82fbfffdc864f\Fody\Removers\MSpecRemover.cs:line 26.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at ModuleWeaver.<>c__DisplayClass19.<CleanTypesBasedOnRemovers>b__17(IRemover x) at c:\TeamCity\buildAgent\work\65b82fbfffdc864f\Fody\ModuleWeaver.cs:line 86.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source, Func`2 predicate)\r [d:\somewhere\some.csproj]
MSBUILD : error :    at ModuleWeaver.CleanTypesBasedOnRemovers() at c:\TeamCity\buildAgent\work\65b82fbfffdc864f\Fody\ModuleWeaver.cs:line 84.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at ModuleWeaver.Execute() at c:\TeamCity\buildAgent\work\65b82fbfffdc864f\Fody\ModuleWeaver.cs:line 55.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at lambda_method(Closure , Object )\r [d:\somewhere\some.csproj]
MSBUILD : error :    at InnerWeaver.ExecuteWeavers(List`1 weaverInstances) at c:\TeamCity\buildAgent\work\7495521761d392b9\FodyIsolated\InnerWeaver.cs:line 90.\r [d:\somewhere\some.csproj]
MSBUILD : error :    at InnerWeaver.Execute() at c:\TeamCity\buildAgent\work\7495521761d392b9\FodyIsolated\InnerWeaver.cs:line 31.\r [d:\somewhere\some.csproj]
MSBUILD : error : Source:\r [d:\somewhere\some.csproj]
MSBUILD : error : Scalpel.Fody\r [d:\somewhere\some.csproj]
MSBUILD : error : TargetSite:\r [d:\somewhere\some.csproj]
MSBUILD : error : Boolean IsMspecField(Mono.Cecil.FieldDefinition)\r [d:\somewhere\some.csproj]
MSBUILD : error :  [d:\somewhere\some.csproj]

[SimonCropp]

fixed and on nuget

[agross]

Thanks!