notice in taxonomy.module: build_mode

If I call taxonomy_link() from within another function like so:

taxonomy_link('taxonomy terms', $node);

Depending on where $node has come from I get the following notice:
notice: Undefined property: stdClass::$build_mode in /Applications/MAMP/htdocs/port/drupal/modules/taxonomy/taxonomy.module on line 52.

The attached patch fixes the notice. Patch is rolled against HEAD but applies with a few lines of offset to D6 as well. Tested and it works fine.