--- mime.tcl.orig	2007-01-10 12:30:22.432000000 +0100
+++ mime.tcl	2007-01-22 13:19:42.841473500 +0100
@@ -3706,6 +3706,7 @@
     }
 
     set string_length [string length $unencoded_string]
+		if { ! $string_length } { return "" }
     set string_bytelength [string bytelength $unencoded_string]
 
     # the 7 is for =?, ?Q?, ?= delimiters of the encoded word
