Check for possible null rect.

core/src/main/java/com/github/weisj/darklaf/ui/text/DarkTextFieldUI.java

@@ -143,6 +143,8 @@ public class DarkTextFieldUI extends DarkTextFieldUIBridge implements PropertyCh
     @Override
     protected Rectangle getVisibleEditorRect() {
         Rectangle rect = super.getVisibleEditorRect();
+        System.out.println(editor);
+        if (rect != null) {
             FontMetrics fm = SwingUtilities2.getFontMetrics(editor, editor.getFont());
             int asc = fm.getMaxAscent();
             Insets ins = editor.getInsets();
@@ -150,6 +152,7 @@ public class DarkTextFieldUI extends DarkTextFieldUIBridge implements PropertyCh
             rect.y = ins.top + (height - asc) / 2;
             rect.y -= fm.getDescent() / 2;
             adjustTextRect(getComponent(), rect);
+        }
         return rect;
     }