Bug 13075: Silence warnings and improve Charset testing.

Calls to C4/Charset.pm's NormalizeString function with an
undefined string were triggering warnings when running:
  prove -v t/db_dependent/Holds.t

Sadly, t/Charset.t was also lacking calls to NormalizeString.

TEST PLAN
---------
1) prove -v t/db_dependent/Holds.t
   -- This should generate the uninitialized string warnings.
      Make sure CPL and MPL are in your branches to save
      yourself from headaches due to expected data.
2) cat t/Charset.t
   -- note there are no function calls to NormalizeString.
      You can see other shortfalls in the tests beyond
      NormalizeString with: grep ^sub C4/Charset.pm
3) prove -v t/Charset.t
4) Apply patch
5) prove -v t/Charset.t
   -- Run as before with more tests.
6) cat t/Charset.t
   -- note there are now function calls to NormalizeString.
7) prove -v t/db_dependent/Holds.t
   -- Nice and clean run! :)
8) koha-qa.pl -v 2 -c 1
   -- all should be Ok.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>

C4/Charset.pm

@@ -179,6 +179,7 @@ Sample code :
 
 sub NormalizeString{
 	my ($string,$nfd,$transform)=@_;
+    return $string unless defined($string); # force scalar context return.
 	utf8::decode($string) unless (utf8::is_utf8($string));
 	if ($nfd){
 		$string= NFD($string);

t/Charset.t

@@ -17,7 +17,7 @@
 
 use Modern::Perl;
 
-use Test::More tests => 11;
+use Test::More tests => 16;
 use MARC::Record;
 
 use utf8;
@@ -27,6 +27,15 @@ BEGIN {
     use_ok('C4::Charset');
 }
 
+my $string;
+ok(!defined(NormalizeString($string,undef,1)),'Uninitialized string case 1 normalizes to uninitialized string.');
+
+$string = 'Sample';
+ok(defined(NormalizeString($string,undef,0)), 'Initialized string case 1 normalizes to some string.');
+ok(defined(NormalizeString($string,undef,1)), 'Initialized string case 2 normalizes to some string.');
+ok(defined(NormalizeString($string,1,0)),     'Initialized string case 3 normalizes to some string.');
+ok(defined(NormalizeString($string,1,1)),     'Initialized string case 4 normalizes to some string.');
+
 my $octets = "abc";
 ok(IsStringUTF8ish($octets), "verify octets are valid UTF-8 (ASCII)");