“WordPress database error” when updating plugin settings

If I try to “Save Changes” on the plugin’s settings page, I get a bunch of database errors (see below). I have the latest version of WordPress and the latest version of the plugin.

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copydate’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copystatus’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copyslug’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copyauthor’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copypassword’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copyattachments’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copychildren’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_copycomments’

WordPress database error: [Column ‘option_value’ cannot be null]
UPDATE wp_options SET option_value = NULL WHERE option_name = ‘duplicate_post_taxonomies_blacklist’