selectValue in DB plugin

[rcamprodon]

selectValue($tableName, $column, $where = null) is implemented as

$stmt = $this->executeSelect($tableName, $column, $where,$afterwhere);
return $stmt->fetchColumn();

$afterwhere is not declared so this gives errors when errors are enabled.
The solution is to replace $afterwhere by ''

Otherwise Atomik is really excellent!