Index: /trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/CheckGroup.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/CheckGroup.java	(revision 17828)
+++ /trunk/src/org/openstreetmap/josm/gui/tagging/presets/items/CheckGroup.java	(revision 17829)
@@ -7,4 +7,5 @@
 import java.util.Map;
 
+import javax.swing.JLabel;
 import javax.swing.JPanel;
 
@@ -35,6 +36,12 @@
         JPanel panel = new JPanel(new GridLayout(rows, columns));
 
+        int i = 0;
         for (Check check : checks) {
             check.addToPanel(panel, support);
+            i++;
+        }
+        for (; i < rows * columns; i++) {
+            // fill remaining cells, see #20792
+            panel.add(new JLabel());
         }