Added initializer for MYOB field

InABox.Poster.MYOB/MYOBGlobalPosterSettings.cs

@@ -11,7 +11,8 @@ public class MYOBGlobalPosterSettings : GlobalPosterSettings
 {
     [EditorSequence(1)]
     [MYOBCompanyFileEditor]
-    public MYOBCompanyFile CompanyFile { get; set; }
+    public MYOBCompanyFile CompanyFile => InitializeField(ref _companyFile, nameof(CompanyFile));
+    private MYOBCompanyFile? _companyFile;
 
     [EditorSequence(2)]
     [TextBoxEditor]