Post-Merge fixes: MT::CMS::Plugin::build_plugin_table dies on call …

…to `$plugin->icon` for any 'pack' addons (i.e. those with `.pack` extensions) since the `MT::Component` package doesn't have an icon function. Whether or not packs should be configurable and listed here is a discussion for another time

lib/MT/CMS/Plugin.pm

@@ -286,7 +286,7 @@ sub build_plugin_table {
 
         if ( my $plugin = $profile->{object} ) {
             my $plugin_icon;
-            if ( $plugin->icon ) {
+            if ( $plugin->can('icon') && $plugin->icon ) {
                 $plugin_icon =
                   $app->static_path . $plugin->envelope . '/' . $plugin->icon;
             }