Index: trunk/src/org/openstreetmap/josm/gui/preferences/advanced/AdvancedPreference.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/advanced/AdvancedPreference.java	(revision 17330)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/advanced/AdvancedPreference.java	(revision 17331)
@@ -492,5 +492,6 @@
             final String prefKeyLower = prefKey.toLowerCase(Locale.ENGLISH);
             final String prefValueLower = prefValue.toLowerCase(Locale.ENGLISH);
-            final boolean canHas = Pattern.compile("\\s+").splitAsStream(txtFilter.getText())
+            String filter = txtFilter.getText(); // see #19825
+            final boolean canHas = filter.isEmpty() || Pattern.compile("\\s+").splitAsStream(filter)
                     .map(bit -> bit.toLowerCase(Locale.ENGLISH))
                     .anyMatch(bit -> {