Bug 557686: PostgreSQL crashes when deleting a custom field of type Date/Time

Bugzilla/Field.pm

@@ -822,17 +822,13 @@ sub remove_from_db {
     }
     else {
         $bugs_query = "SELECT COUNT(*) FROM bugs WHERE $name IS NOT NULL";
-        if ($self->type != FIELD_TYPE_BUG_ID) {
+        if ($self->type != FIELD_TYPE_BUG_ID && $self->type != FIELD_TYPE_DATETIME) {
             $bugs_query .= " AND $name != ''";
         }
         # Ignore the default single select value
         if ($self->type == FIELD_TYPE_SINGLE_SELECT) {
             $bugs_query .= " AND $name != '---'";
         }
-        # Ignore blank dates.
-        if ($self->type == FIELD_TYPE_DATETIME) {
-            $bugs_query .= " AND $name != '00-00-00 00:00:00'";
-        }
     }
 
     my $has_bugs = $dbh->selectrow_array($bugs_query);