don't unset action on labels from getSelectedLabel

Now, that we're using objects, here we modify the reference to the object, so we
should define if we do not want $action data member on VersioncontrolLabel
object.

For example, following commitlog_operation():
    - see how operation object changes after calling theme_commitlog_operation_items():
        - which calls theme_commitlog_item():
            - which calls versioncontrol_get_url_item_log_view():
                - which calls VerisoncontrolItem::getSelectedLabel():
                    - which unset action data member
    - and then on theme_commitlog_operation_caption():
        - we use VersioncontrolLabel action data member already unset before, so
          it fail at build correctly the $labels_by_type array and then no
          branches are shown

So, this in an attempt after 2 days looking for the problem of avoiding 2
notices! :p

includes/VersioncontrolItem.php

@@ -473,7 +473,8 @@ public function getSelectedLabel() {
         // Just to make sure that we only pass applicable info:
         // 'action' might make sense in an operation, but not in an item array.
         if (isset($selected_label->action)) {
-          unset($selected_label->action);
+        //FIXME we are returning a label here, not an item; so, is it ok to have an action on label?
+        //  unset($selected_label->action);
         }
         $selected_label->ensure();
         $this->selected_label->label = $selected_label;