Bug 711925: Update from 4.0 or older to 4.2 or trunk fails when bug_see_also field is populated

Bugzilla/DB/Schema.pm

@@ -502,7 +502,7 @@ use constant ABSTRACT_SCHEMA => {
                                       COLUMN => 'bug_id',
                                       DELETE => 'CASCADE'}},
             value  => {TYPE => 'varchar(255)', NOTNULL => 1},
-            class  => {TYPE => 'varchar(255)', NOTNULL => 1},
+            class  => {TYPE => 'varchar(255)', NOTNULL => 1, DEFAULT => "''"},
         ],
         INDEXES => [
             bug_see_also_bug_id_idx => {FIELDS => [qw(bug_id value)], 

Bugzilla/Install/DB.pm

@@ -3572,7 +3572,7 @@ sub _populate_bug_see_also_class {
     }
 
     $dbh->bz_add_column('bug_see_also', 'class',
-        {TYPE => 'varchar(255)', NOTNULL => 1}, '');
+        {TYPE => 'varchar(255)', NOTNULL => 1, DEFAULT => "''"}, '');
 
     my $result = $dbh->selectall_arrayref(
         "SELECT id, value FROM bug_see_also");