Index: /trunk/src/org/openstreetmap/josm/gui/io/UploadDialog.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/io/UploadDialog.java	(revision 10104)
+++ /trunk/src/org/openstreetmap/josm/gui/io/UploadDialog.java	(revision 10105)
@@ -509,5 +509,5 @@
             if (!s.isEmpty()) {
                 UnicodeBlock block = Character.UnicodeBlock.of(s.charAt(0));
-                if (block.toString().contains("CJK")) {
+                if (block != null && block.toString().contains("CJK")) {
                     result = s.length() < 4;
                 } else {
Index: /trunk/test/unit/org/openstreetmap/josm/gui/io/UploadDialogTest.java
===================================================================
--- /trunk/test/unit/org/openstreetmap/josm/gui/io/UploadDialogTest.java	(revision 10104)
+++ /trunk/test/unit/org/openstreetmap/josm/gui/io/UploadDialogTest.java	(revision 10105)
@@ -104,4 +104,6 @@
         assertFalse(UploadDialog.UploadAction.isUploadCommentTooShort("geometric corrections"));
         assertFalse(UploadDialog.UploadAction.isUploadCommentTooShort("几何校正"));
+        // test with unassigned unicode characters ==> no unicode block
+        assertTrue(UploadDialog.UploadAction.isUploadCommentTooShort("\u0860"));
     }
 }