Potential fix for code scanning alert no. 200: Nested 'if' statements can be combined

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: csharpfritz

src/BlazorWebFormsComponents/CustomControls/HtmlTextWriter.cs

@@ -71,13 +71,13 @@ public void AddAttribute(string name, string value)
 				throw new ArgumentNullException(nameof(name));
 
 			// Special handling for class attribute - concatenate instead of replace
-			if (name.Equals("class", StringComparison.OrdinalIgnoreCase) && _pendingAttributes.TryGetValue("class", out var existingClass))
+			if (name.Equals("class", StringComparison.OrdinalIgnoreCase)
+				&& _pendingAttributes.TryGetValue("class", out var existingClass)
+				&& !string.IsNullOrEmpty(existingClass)
+				&& !string.IsNullOrEmpty(value))
 			{
-				if (!string.IsNullOrEmpty(existingClass) && !string.IsNullOrEmpty(value))
-				{
-					_pendingAttributes["class"] = $"{existingClass} {value}";
-					return;
-				}
+				_pendingAttributes["class"] = $"{existingClass} {value}";
+				return;
 			}
 
 			_pendingAttributes[name] = value ?? string.Empty;