When the registry key does not exist use the light theme. (#3531)

This is an alternate fix to the one that was originally provided for #3526.

Author: Keboo

MaterialDesignThemes.UITests/WPF/TreeListViews/TreeListViewTests.cs

@@ -236,12 +236,12 @@ public async Task CanMoveTopLevelElementDown()
 
         IVisualElement<TreeListViewItem> secondItem = await treeListView.GetElement<TreeListViewItem>("/TreeListViewItem[1]");
 
-        //Move item
+        await secondItem.LeftClick();
         await Wait.For(async () =>
         {
-            await secondItem.LeftClick();
             return await secondItem.GetIsSelected();
         });
+        //Move item
         await moveDownButton.LeftClick();
 
         await AssertTreeItemContent(treeListView, 0, "0");
@@ -1004,7 +1004,7 @@ public async Task TreeListView_WithCollectionView_RendersItems()
     }
 
     [Fact]
-    public async Task TreeListView_AddingExpandedItemWithChildren_ShowsExpanedItem()
+    public async Task TreeListView_AddingExpandedItemWithChildren_ShowsExpandedItem()
     {
         await using var recorder = new TestRecorder(App);
 

MaterialDesignThemes.Wpf/ThemeExtensions.cs

@@ -43,12 +43,12 @@ public static void SetBaseTheme(this Theme theme, BaseTheme baseTheme)
             default:
                 switch (Theme.GetSystemTheme())
                 {
-                    case BaseTheme.Light:
-                        SetLightTheme(theme);
-                        break;
                     case BaseTheme.Dark:
                         SetDarkTheme(theme);
                         break;
+                    default:
+                        SetLightTheme(theme);
+                        break;
                 }
                 break;
         }