Bug 8880 - Uninitialized variables trigger error log entries

Simply by logging in, clicking Circulation, clicking the
'Check out' link, error log entries were generated.

This patch ensures $findborrower, $barcode, and $print are all
initialized by adding "|| q{}" onto their initializations.
This reduces the silent error log entries generated.

As this patch would overlap with bug 8826 in the initialization
of hashes to prevent other error logs, those changes are in this
patch. Applying this patch without having applied the patch for
bug 8826.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Passed-QA-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>

circ/circulation.pl

@@ -101,7 +101,7 @@ my @failedreturns = $query->param('failedreturn');
 our %return_failed = ();
 for (@failedreturns) { $return_failed{$_} = 1; }
 
-my $findborrower = $query->param('findborrower');
+my $findborrower = $query->param('findborrower') || q{};
 $findborrower =~ s|,| |g;
 my $borrowernumber = $query->param('borrowernumber');
 
@@ -122,7 +122,7 @@ if (C4::Context->preference("UseTablesortForCirc")) {
     $template->param(UseTablesortForCirc => 1);
 }
 
-my $barcode        = $query->param('barcode') || '';
+my $barcode        = $query->param('barcode') || q{};
 $barcode =~  s/^\s*|\s*$//g; # remove leading/trailing whitespace
 
 $barcode = barcodedecode($barcode) if( $barcode && C4::Context->preference('itemBarcodeInputFilter'));
@@ -131,7 +131,7 @@ my $duedatespec    = $query->param('duedatespec')   || $session->param('stickydu
 my $issueconfirmed = $query->param('issueconfirmed');
 my $cancelreserve  = $query->param('cancelreserve');
 my $organisation   = $query->param('organisations');
-my $print          = $query->param('print');
+my $print          = $query->param('print') || q{};
 my $newexpiry      = $query->param('dateexpiry');
 my $debt_confirmed = $query->param('debt_confirmed') || 0; # Don't show the debt error dialog twice