Issue when creating a new blog article on 18.3

[BondForWebSolutions]

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Current Behavior / Expected Behavior

I just upgrade 2sxc to version 18.3 and tried to add a new blog article (blog 6.17.0).
And I saw these guids in the dropdowns:

When I click on save the blog renders in de list with an error:

The text of the error is:
"
Error: System.NullReferenceException: De objectverwijzing is niet op een exemplaar van een object ingesteld.
bij ToSic.Eav.Data.EntityWrapper.FindPropertyInternal(PropReqSpecs specs, PropertyLookupPath path) in C:\Projects\2sxc\eav-server\ToSic.Eav.Core\Data\Entities\EntityWrapper.cs:regel 161
bij ToSic.Sxc.Data.Internal.PropLookupWithPathEntity.FindPropertyInternal(PropReqSpecs specs, PropertyLookupPath path) in C:\Projects\2sxc\2sxc\Src\Sxc\ToSic.Sxc\Data\Internal\PropertyLookup\PropLookupWithPathEntity.cs:regel 24
bij ToSic.Sxc.Data.Internal.Dynamic.GetAndConvertHelper.GetInternal(String field, String language, Boolean lookupLink) in C:\Projects\2sxc\2sxc\Src\Sxc\ToSic.Sxc\Data\Internal\Dynamic\GetAndConvertHelper.cs:regel 94
bij ToSic.Sxc.Data.Internal.Dynamic.CodeItemHelper.G4T[TValue](String name, NoParamOrder noParamOrder, TValue fallback, Nullable1 required, String cName) in C:\Projects\2sxc\2sxc\Src\Sxc\ToSic.Sxc\Data\Internal\Dynamic\CodeItemHelper.cs:regel 45 bij ToSic.Sxc.Data.Internal.Dynamic.CodeItemHelper.String(String name, NoParamOrder noParamOrder, String fallback, Nullable1 required, Object scrubHtml) in C:\Projects\2sxc\2sxc\Src\Sxc\ToSic.Sxc\Data\Internal\Dynamic\CodeItemHelper.cs:regel 71
bij AppCode.Data.AutoGenerated.ZagAuthor.get_FullName()
bij RazorHost.RazorViewauthordateandcategories.Execute() in [PATH TO:]\2sxc\blog6\bs5\parts\authordateandcategories.cshtml🎯:regel 10
bij System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
bij System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
bij ToSic.Sxc.Dnn.Razor.Internal.DnnRazorCompiler.Render(RazorComponentBase page, TextWriter writer, Object data) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Dnn\Razor\Internal\DnnRazorCompiler.cs:regel 77
--- Einde van stacktracering vanaf vorige locatie waar uitzondering is opgetreden ---
bij System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
bij ToSic.Sxc.Dnn.Razor.Internal.DnnRazorCompiler.Render(RazorComponentBase page, TextWriter writer, Object data) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Dnn\Razor\Internal\DnnRazorCompiler.cs:regel 84
bij ToSic.Sxc.Dnn.Razor.Internal.DnnRazorCompiler.RenderImplementation(RazorComponentBase webpage, RenderSpecs specs) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Dnn\Razor\Internal\DnnRazorCompiler.cs:regel 93
bij ToSic.Sxc.Dnn.Razor.Internal.DnnRazorCompiler.RenderSubPage(RazorComponentBase parent, String templatePath, Object data) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Dnn\Razor\Internal\DnnRazorCompiler.cs:regel 212
bij ToSic.Sxc.Dnn.Razor.HtmlHelper.RenderWithRoslynOrClassic(String path, Object data) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Dnn\Razor\HtmlHelper.cs:regel 109
bij ToSic.Sxc.Dnn.Razor.HtmlHelper.Partial(String path, Object data) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Dnn\Razor\HtmlHelper.cs:regel 57
"

Instructions to Reproduce the Problem

Upgrade to 2sxc 18.3 and add a new blog entry

Your environment

DNN 09.13.04
2sxc 18.03.00
Blog 6.17.0

[BondForWebSolutions]

I also tried to modify the generated code from:
public string FullName => _item.String("FullName", fallback: "");

To somthing like:
public string FullName => _item != null && _item.ContainsKey("FullName") ? _item.String("FullName") : "";

But that didn't really help...

[iJungleboy]

I have a feeling that this is a bug in the form prefill.

Could you verify that

1. previous blogs still work
2. only new posts fail
3. new posts - when saving and re-opening - probably have an empty field in those two dropdowns?

[trouble2]

That is correct (1,2 and 3).
I've seen this behaviour more on other installs (18.1, 18.2 and 18.3)
Looks to me like it shows the values instead of the text for the dropdowns, but I don't know if that is true.
Since you're working on the pickers in the last couple of versions I suspect it has something to do with those modifications.

Also for example in the admin interface (this screenshot is from 18.0.0):