Fix bug submodel descriptors

Author: aorzelskiGH

src/AasxServerBlazor/Properties/launchSettings.json

@@ -10,7 +10,7 @@
     },
     "AasxServerBlazor": {
       "commandName": "Project",
-      "commandLineArgs": "--with-db --start-index 1000 --no-security --save-temp 30 --secret-string-api 1234 --aasx-in-memory 7 --data-path \"C:\\Development\\aasxs-repository\" --edit --external-blazor http://localhost:5001",
+      "commandLineArgs": "--start-index 0 --no-security --save-temp 30 --secret-string-api 1234 --aasx-in-memory 20 --data-path \"C:\\Development\\aasxs-repository\" --edit --external-blazor http://localhost:5001",
       "launchBrowser": true,
       "environmentVariables": {
         "ASPNETCORE_ENVIRONMENT": "Development",

src/IO.Swagger.Registry.Lib.V3/Controllers/AssetAdministrationShellRegistryAPIApi.cs

@@ -244,9 +244,12 @@ where true
         List<SubmodelDescriptor> submodelDescriptors = [];
         foreach (var ad in aasDescriptors)
         {
-            foreach (var sd in ad.SubmodelDescriptors)
+            if (ad != null && ad.SubmodelDescriptors != null)
             {
-                submodelDescriptors.Add(sd);
+                foreach (var sd in ad.SubmodelDescriptors)
+                {
+                    submodelDescriptors.Add(sd);
+                }
             }
         }