Fix network cache size for first run
QNetworkDiskCache will take care of creating a directory if it doesn't exist. QStorageInfo on a directory that doesn't exist will return that it has 0 bytesTotal.
As well as being potentially inefficient for the second run, it has been reported that a QNetworkDiskCache of 0 causes out of bounds memory writes.
(cherry picked from commit 90e271b9)