workbench_moderation missing column is_current - cause is schema version in system table set to -1 despite module being enabled - no updates will run [#2563133]

Hello,

I've just discovered a weird bug in my workbench moderation module, where the schema version is set to -1 despite the module being enabled.

This has resulted in none of the module's database updates running.

I'm not sure whether this is a bug in how the site I'm working on has been set up, or something in the module itself, but it was easily enough fixed in a small update script in a custom module; if this issue has affected other users, maybe this check could be incorporated into the module's hook_init(), so that the next time the database is updated the schema updates can run correctly?

Hopefully this will help somebody else experiencing weird errors like me :)

For example...

  function workbench_moderation_init() {
    /**
     * Change schema version of workbench moderation module to 0 if it's
     * -1 - otherwise, schema updates will not run and we will encounter fatal DB
     * errors, e.g. missing column "is_current". :(
     *
     * Note: you will need to run the database updates script to catch any
     * remaining updates.
     */
    if (!variable_get('workbench_moderation_schema_check', FALSE)) {
      db_update('system')
        ->fields(array('schema_version' => 0))
        ->condition('name', 'workbench_moderation')
        ->condition('schema_version', -1)
        ->condition('status', 1)
        ->execute();

      variable_set('workbench_moderation_schema_check', TRUE);
    }

This resulted in the following Drush output when I re-ran drush updatedb:

 Cs_settings  7102  Change schema version of workbench moderation module to 0 if it's  -1 - otherwise, schema updates will not run and we 
                    will encounter fatal DB  errors, e.g. missing column "is_current". :(   Note: you will need to re-run the database    
                    updates script to catch any  remaining updates.
Do you wish to run all pending updates? (y/n): y
Changed schema version of workbench moderation module to 0 if it's -1 - otherwise, schema updates will not run and we will         [ok]
encounter fatal DB errors, e.g. missing column "is_current". :( Note: you will need to re-run the database updates script to catch
any remaining updates.
Performed update: cs_settings_update_7102                                                                                          [ok]
'all' cache was cleared.                                                                                                           [success]
Finished performing updates.                                                                                                       [ok]
 Workbench_moderation  7001  Update the 'weight' field on {workbench_moderation_states}.   Accept standard Drupal weight values.  
 Workbench_moderation  7002  Drop the unused 'ntypes' field from workbench_moderation_transitions.                                
 Workbench_moderation  7003  Use "revision" instead of "version" when referring to node revisions.                                
 Workbench_moderation  7004  Use "Published" instead of "Publish" and "Needs Review" instead of "Review" for state names.         
 Workbench_moderation  7005  Shorten descriptions for default states                                                              
 Workbench_moderation  7006  Add machine names to moderation states.                                                              
 Workbench_moderation  7007  Replace the "Unpublish the current live revision" permission with a transition.                      
 Workbench_moderation  7008  Fix the not null column schema for {workbench_moderation_states}.name.                               
 Workbench_moderation  7009  Add new fields to workbench_moderation_transitions table.                                            
 Workbench_moderation  7010  Comply with SQL-99:  Rename the 'current' column to 'is_current'.
Do you wish to run all pending updates? (y/n): y
Updated the weight field on the moderation states table.                                                                           [ok]
Performed update: workbench_moderation_update_7001                                                                                 [ok]
Dropped unused field from the moderation transitions table.                                                                        [ok]
Performed update: workbench_moderation_update_7002                                                                                 [ok]
The renamed permission was updated for 0 roles.                                                                                    [ok]
Performed update: workbench_moderation_update_7003                                                                                 [ok]
Updated state names and transitions.                                                                                               [ok]
Performed update: workbench_moderation_update_7004                                                                                 [ok]
Updated state descriptions.                                                                                                        [ok]
Performed update: workbench_moderation_update_7005                                                                                 [ok]
Cannot add field workbench_moderation_states.label: field already exists.                                                          [error]
Performed update: workbench_moderation_update_7006                                                                                 [ok]
'all' cache was cleared.                                                                                                           [success]
Finished performing updates.                                                                                                       [ok]