[Mimedefang] Use of uninitialized value

[Breena Kermott]

I keep getting the following error message in my logs:

Aug 12 11:54:12 azriel mimedefang-multiplexor: Slave 5 stderr: Use of 
uninitialized value in concatenation (.) at /usr/local/bin/mimedefang.pl 
line 3640, <IN> line 19.
Aug 12 11:54:12 azriel mimedefang-multiplexor: Slave 5 stderr: Use of 
uninitialized value in concatenation (.) at /usr/local/bin/mimedefang.pl 
line 3640, <IN> line 24.
Aug 12 11:54:12 azriel mimedefang-multiplexor: Slave 5 stderr: Use of 
uninitialized value in concatenation (.) at /usr/local/bin/mimedefang.pl 
line 3640, <IN> line 25.

Perhaps we just need to check a variable before trying to use it, but it 
might be a symptom of an actual problem. Anyone know?