Fix CDTEXT processing

K3bDevice::CdText::textForPackType returns link to a destructed object
Additionally, same issue was fixed for AudioEncoder module

Signed-off-by: Mashiro <m.t.0x73@gmail.com>

libk3b/plugin/k3baudioencoder.cpp

@@ -91,7 +91,7 @@ const TQString& K3bAudioEncoder::filename() const
   if( d->outputFile )
     return d->outputFilename;
   else
-    return TQString();
+    return TQString::null;
 }
 
 

libk3bdevice/k3bcdtext.cpp

@@ -524,7 +524,7 @@ const TQString& K3bDevice::CdText::textForPackType( int packType, unsigned int t
     if( track == 0 )
       return discId();
     else 
-      return TQString();
+      return TQString::null;
 
 //   case 0x87:
 //     if( track == 0 )