Replaces return"" by return QString()
Replaces return"" by return QString()

It's faster and cleaner.
        QString().isEmpty();            // returns true
        QString().isNull();             // returns true
So replacing "" by QString() will not brake existing code.

Signed-off-by: Luís Pereira <95d1463b1ff9eef535e39fb0d755bc242cfcea61@gmail.com>

lxde/liblxqt-mount