Index: openacs-4/packages/xowiki/tcl/xowiki-form-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/xowiki-form-procs.tcl,v
diff -u -N -r1.134.2.11 -r1.134.2.12
--- openacs-4/packages/xowiki/tcl/xowiki-form-procs.tcl	4 May 2017 07:04:07 -0000	1.134.2.11
+++ openacs-4/packages/xowiki/tcl/xowiki-form-procs.tcl	9 May 2017 14:09:28 -0000	1.134.2.12
@@ -171,7 +171,8 @@
     $form instvar data
     $form get_uploaded_file
     set data [$form set data]
-    if {[virus check [$data set import_file]]} {
+    if {[$data exists import_file] &&
+        [virus check [$data set import_file]]} {
       util_user_message -message "uploaded file contains a virus; upload rejected"
       return 0
     }