Fix compiler warning about unused parameter

Fix gcc compiler warning about unused parameter:

qquickwindow.cpp:111:10: warning: unused parameter ‘e’ [-Wunused-parameter]

This got introduced by commit 9d75626b



Change-Id: Ia280fd9fdd584eed81f4d810311c56f5daee3e28
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>