installing volunteer module without event module breaks drupal

If the volunteer module is enabled without the event module also enabled, then making any kind of content contribution gives the error:

Fatal error: Call to undefined function: event_is_enabled() in /workgroups/webdev/communitycasestudies.crcresearch.org/modules/volunteer/volunteer.module on line 761

Thus most of the drupal installation is broken without a good clue to the inexperienced administrator as to what the problem is.