Use of uninitialized value in String

[Anish Kumar K.]

I am getting this  error not sure why
   Use of uninitialized value in string eq at line :6


1: $rows=$dbh->prepare("select browsername from  course where clientname 
='DEMO");
2: $rows->execute();
3: while(@row=$rows->fetchrow_array())
4: {
5:   $browserName=shift(@row);
6:   if ($browserName eq "")
7:   {
8:     ++$browserHash{"EMPTY_BROWSER"};
9:  }
10:   else
11:  {
12:    ++$browserHash{$browserName};
13:  }
14: }


Why this is happening ...The hash is like this

%browserHash=(
        "IE"=>0,
        "NETSCAPE"=>0,
        "FIREFOX"=>0,
        "OTHER"=>0,
        "EMPTY_BROWSER"=>0
);