Index: openacs-4/packages/xowiki/tcl/package-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/package-procs.tcl,v
diff -u -r1.332.2.101 -r1.332.2.102
--- openacs-4/packages/xowiki/tcl/package-procs.tcl	14 Dec 2021 13:55:26 -0000	1.332.2.101
+++ openacs-4/packages/xowiki/tcl/package-procs.tcl	27 Dec 2021 17:03:22 -0000	1.332.2.102
@@ -182,8 +182,10 @@
   # URL and naming management
   #
   Package instproc split_name {string} {
-    set prefix ""
     regexp {^([a-z][a-z]|file|image|video|audio|js|css|swf|folder):(.*)$} $string _ prefix suffix
+    if {![info exists prefix] || ![info exists suffix]} {
+      error "cannot split name '$string' into a prefix and a suffix"
+    }
     return [list prefix $prefix suffix $suffix]
   }
   Package instproc join_name {{-prefix ""} -name} {