minor fix

com.unity.uiwidgets/Runtime/ui/text.cs

         }
 
         public void addPlaceholder(float width, float height, PlaceholderAlignment alignment,
-            TextBaseline baseline,
+            TextBaseline? baseline,
-            D.assert(alignment == PlaceholderAlignment.aboveBaseline ||
+            D.assert((alignment == PlaceholderAlignment.aboveBaseline ||
-                     alignment == PlaceholderAlignment.baseline);
+                     alignment == PlaceholderAlignment.baseline) ? baseline != null : true);
-                (int) baseline);
+                (int) (baseline ?? TextBaseline.alphabetic));
             placeholderCount++;
             placeholderScales.Add(item: scale);
         }