[MERGE] many2many_tags: correctly checks it's falsy value

bzr revid: fme@openerp.com-20121121100812-gzn25f8g50cr5t3t

diff --cc addons/web/static/src/js/view_form.js
index d7b3a68,7ae4221..ac54df6
--- 1/addons/web/static/src/js/view_form.js
--- 2/addons/web/static/src/js/view_form.js
+++ b/addons/web/static/src/js/view_form.js
@@@ -4026,9 -4026,11 +4026,12 @@@ instance.web.form.FieldMany2ManyTags = 
          }
          this._super(value_);
      },
+     is_false: function() {
+         return _(this.get("value")).isEmpty();
+     },
      get_value: function() {
 -        return [commands.replace_with(this.get("value"))];
 +        var tmp = [commands.replace_with(this.get("value"))];
 +        return tmp;
      },
      get_search_blacklist: function() {
          return this.get("value");