Index: openacs-4/packages/xowiki/tcl/form-field-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/form-field-procs.tcl,v
diff -u -r1.89 -r1.90
--- openacs-4/packages/xowiki/tcl/form-field-procs.tcl	9 Sep 2008 12:46:45 -0000	1.89
+++ openacs-4/packages/xowiki/tcl/form-field-procs.tcl	9 Sep 2008 13:18:23 -0000	1.90
@@ -1286,7 +1286,9 @@
   youtube_url set urlre {^http://www.youtube.com/watch[?]v=(.*)$}
   
   youtube_url instproc pretty_value {v} {
-    if {[regexp [[self class] set urlre] $v _ name]} {
+    if {$v eq ""} {
+      return ""
+    } elseif {[regexp [[self class] set urlre] $v _ name]} {
       return "<object width='425' height='344'>
 <param name='movie' value='http://www.youtube.com/v/$name&fs=1'></param>
 <param name='allowFullScreen' value='true'></param>