Avoid Imager exceptions when creating thumbnails.

We were telling it to just warn, but then trying to write out a non-existant file [#146: resolved].

lib/Bric/Biz/Asset/Business/Media/Image.pm

@@ -695,7 +695,7 @@ sub find_or_create_alternate {
 =item my $created_ok = $image->create_thumbnail
 
 Creates a thumbnail image from the supplied image object. Returns 1 on
-successful completion or error string if it fails.
+successful completion and C<undef> on failure.
 
 B<Throws:> NONE.
 
@@ -724,7 +724,7 @@ sub create_thumbnail {
                 type    => 'min',
             );
         },
-    });
+    }) or return;
 
     # Save the image or die.
     my $thumbfile = $self->_thumb_file;

lib/Bric/Changes.pod

@@ -1,3 +1,5 @@
+=encoding utf8
+
 =head1 Name
 
 Bric::Changes - Bricolage Changes
@@ -191,6 +193,12 @@ The validation of code select field code is now consistent between the element
 type profile, the field type profile, and the SOAP element type interface.
 Thanks to Krzysztof Rudnik for the report (Bug #140). [David]
 
+=item *
+
+Media no longer throw the exception “Can't call method "write" on an undefined
+value” when L<Imager> is doesn't recognize an image file format. Thanks to
+Matt Rolf for the report (Bug #146). [David]
+
 =back
 
 =head1 Version 1.11.3 (2010-01-28)