fix(ui): Add logging and hardening around slide out of range error

Fixes #49

LogoSlideMaker.WinUi/ViewModels/MainViewModel.cs

@@ -642,7 +642,22 @@ private void PopulateLayout()
             return;
         }
 
-        var variant = _definition.Variants.Count > 0 ? _definition.Variants[_slideNumber] : new Variant();
+        var existingVariants = _definition.Variants;
+        var slideNumber = _slideNumber;
+
+        // In case of no variants, we'll use a blank
+        if (existingVariants.Count == 0)
+        {
+            existingVariants = [new()];
+        }
+
+        if (slideNumber >= existingVariants.Count)
+        {
+            logWarningSlideOutoFoRange(slideNumber, existingVariants.Count);
+            slideNumber = 0;
+        }
+
+        var variant = existingVariants[slideNumber];
 
         var engine = new LayoutEngine(_definition, variant);
         _layout = engine.CreateSlideLayout();
@@ -736,5 +751,8 @@ private void OnPropertyChanged([CallerMemberName] string? propertyName = null)
     [LoggerMessage(Level = LogLevel.Error, Message = "{Location}: Slide number {Number} out of range {Count}")]
     public partial void logFailSlideOutoFoRange(int number, int count, [CallerMemberName] string? location = null);
 
+    [LoggerMessage(Level = LogLevel.Warning, Message = "{Location}: Slide number {Number} out of range {Count}")]
+    public partial void logWarningSlideOutoFoRange(int number, int count, [CallerMemberName] string? location = null);
+
     #endregion
 }