Index: trunk/src/org/openstreetmap/josm/gui/tagging/ac/AutoCompletingComboBox.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/tagging/ac/AutoCompletingComboBox.java	(revision 13572)
+++ trunk/src/org/openstreetmap/josm/gui/tagging/ac/AutoCompletingComboBox.java	(revision 13573)
@@ -104,5 +104,10 @@
             if (selecting)
                 return;
-            super.remove(offs, len);
+            try {
+                super.remove(offs, len);
+            } catch (IllegalArgumentException e) {
+                // IAE can happen with Devanagari script, see #15825
+                Logging.error(e);
+            }
         }