Fix warning for -no-feature-lineedit

Change-Id: Ia56d5d7266a379f911e4db61e60b8b39af5b6342
Reviewed-by: Stephan Binner <stephan.binner@basyskom.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/widgets/itemviews/qabstractitemdelegate.cpp

@@ -547,6 +547,8 @@ bool QAbstractItemDelegatePrivate::tryFixup(QWidget *editor)
             return e->hasAcceptableInput();
         }
     }
+#else
+    Q_UNUSED(editor)
 #endif // QT_NO_LINEEDIT
 
     return true;