process_command does not properly skip blank input lines

Upstream bug report filed at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=651642

This is related to Debian bug reports #630772 and #637737

When purging old kernels from the command line, multiple "Use of uninitialized value $command" errors are displayed. These errors are caused by the following code line:

      return 1 unless defined && ! /^\s*#/; # Skip blank lines, comments.

The code skips undefined input and comments, but the associated inline comment claims that the intent was to skip blank lines and comments. I resolved the problem locally by making the following change:

diff --git a/Debconf/ConfModule.pm b/Debconf/ConfModule.pm
index 8017202..20c084e 100644
--- a/Debconf/ConfModule.pm
+++ b/Debconf/ConfModule.pm
@@ -228,7 +228,9 @@ sub process_command {
  my $this=shift;

  debug developer => "<-- $_";
- return 1 unless defined && ! /^\s*#/; # Skip blank lines, comments.
+ return 1 unless defined; # Skip empty input.
+ return 1 if /^\s*$/ # Skip blank lines.
+ return 1 if /^\s*#/ # Skip comments.
  chomp;
  my ($command, @params);
  if (defined $this->client_capb and grep { $_ eq 'escape' } @{$this->client_capb}) {

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: debconf 1.5.40ubuntu1 [modified: usr/share/perl5/Debconf/ConfModule.pm]
Uname: Linux 3.2.0-rc5+ i686
ApportVersion: 1.23-0ubuntu4
Architecture: i386
Date: Sat Dec 10 15:18:59 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Alpha i386 (20100712)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: debconf
UpgradeStatus: No upgrade log present (probably fresh install)