Remove bogus call and comment from addressbook

QMap::empty() does not empty the list but is the STL
version to ask if the map is empty. Remove the comment
and code as operator>> of QDataStream will clear the
map.

Fixes Coverity CID#89073

Change-Id: I259e518b44afd42b698368b42aedcc3b84240aca
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

examples/widgets/tutorials/addressbook/part7/addressbook.cpp

@@ -370,7 +370,6 @@ void AddressBook::loadFromFile()
 
         QDataStream in(&file);
         in.setVersion(QDataStream::Qt_4_3);
-        contacts.empty();   // empty existing contacts
         in >> contacts;
 
         QMap<QString, QString>::iterator i = contacts.begin();