Don't pass null values for background rendering to user defined renderers.

core/src/main/java/com/github/weisj/darklaf/ui/list/DarkListCellRendererDelegate.java

@@ -27,10 +27,14 @@ import javax.swing.*;
 
 import com.github.weisj.darklaf.delegate.ListCellRendererDelegate;
 import com.github.weisj.darklaf.ui.cell.CellUtil;
+import com.github.weisj.darklaf.util.LazyValue;
 import com.github.weisj.darklaf.util.PropertyUtil;
 
 public class DarkListCellRendererDelegate extends ListCellRendererDelegate<Object> implements SwingConstants {
 
+    private static final LazyValue<DefaultListCellRenderer> DEFAULT_RENDERER =
+            new LazyValue<>(DefaultListCellRenderer::new);
+
     public DarkListCellRendererDelegate() {
         super(null);
     }
@@ -38,7 +42,7 @@ public class DarkListCellRendererDelegate extends ListCellRendererDelegate<Objec
     @Override
     public void setDelegate(final ListCellRenderer<Object> delegate) {
         if (delegate == null) {
-            super.setDelegate(new DefaultListCellRenderer());
+            super.setDelegate(DEFAULT_RENDERER.get());
         } else {
             super.setDelegate(delegate);
         }

core/src/main/java/com/github/weisj/darklaf/ui/list/DarkListUI.java

@@ -184,8 +184,14 @@ public class DarkListUI extends DarkListUIBridge implements CellConstants {
         int cw = empty && bgWidth > 0 ? bgWidth : rowBounds.width;
         int ch = rowBounds.height;
 
+        ListCellRenderer<Object> renderer = cellRenderer;
+        if (empty) {
+            rendererDelegate.setDelegate(null);
+            renderer = rendererDelegate;
+        }
+
         Component rendererComponent =
-                cellRenderer.getListCellRendererComponent(list, value, cellIndex, isSelected, cellHasFocus);
+                renderer.getListCellRendererComponent(list, value, cellIndex, isSelected, cellHasFocus);
         rendererPane.paintComponent(g, rendererComponent, list, cx, cy, cw, ch, true);
     }
 

core/src/test/java/icon/AllIcons.java

@@ -152,10 +152,8 @@ public class AllIcons implements ComponentDemo {
         public Component getListCellRendererComponent(final JList<? extends Pair<String, ? extends Icon>> list,
                 final Pair<String, ? extends Icon> value, final int index, final boolean isSelected,
                 final boolean cellHasFocus) {
-            if (value != null) {
-                setIcon(value.getSecond());
-                setText(value.getFirst());
-            }
+            setIcon(value.getSecond());
+            setText(value.getFirst());
             return this;
         }
     }