Core - Corrected disposable pattern usage

Core - Further nullable refactoring..

src/Artemis.UI.Shared/DataModelVisualization/Shared/DataModelListPropertiesViewModel.cs

@@ -29,7 +29,7 @@ namespace Artemis.UI.Shared
             set => SetAndNotify(ref _listType, value);
         }
 
-        public object DisplayValue
+        public new object DisplayValue
         {
             get => _displayValue;
             set => SetAndNotify(ref _displayValue, value);

src/Artemis.UI.Shared/Utilities/PluginUtilities.cs

@@ -39,8 +39,6 @@ namespace Artemis.UI.Shared
             if (parsedIcon == false)
                 iconEnum = PackIconKind.QuestionMarkCircle;
             return iconEnum;
-
-            return icon;
         }
     }
 }