ZF-5204: Using fetchCol on result where first item is empty results in empty array

Description

select distinct x from y yields an empty array if the data in the first field returned is an empty string. Example data ['',1,2,3].

Comments

Problem occurs at Zend/Db/Statement.php {{328: while ($val = $this->fetchColumn($col)) {}}

Since fetchColumn returns false when there is no more results (and false cannot be an SQL value), the following corrects the problem. {{328: while (false !== ($val = $this->fetchColumn($col))) {}}

It duplicates ZF-2112