Invalidate OutputPanel on style change

Fixes an incorrect height staying cached on font change.

RELEASE-NOTES.md

@@ -48,6 +48,7 @@ END TEMPLATE-->
 * Fix `Menu` and `NumpadDecimal` key codes on SDL3.
 * Fix modifying `Label.FontOverride` not causing a layout update.
 * Controls created by rich-text tags now get arranged to a proper size.
+* Fix `OutputPanel` scrollbar breaking if a style update changes the font size.
 
 ### Other
 

Robust.Client/UserInterface/Controls/OutputPanel.cs

@@ -336,6 +336,14 @@ namespace Robust.Client.UserInterface.Controls
             base.UIScaleChanged();
         }
 
+        protected override void StylePropertiesChanged()
+        {
+            base.StylePropertiesChanged();
+
+            // Font may have changed.
+            _invalidateEntries();
+        }
+
         internal static float GetScrollSpeed(Font font, float scale)
         {
             return font.GetLineHeight(scale) * 2;