Since commit 9ab043b6 we're checking for invalid file paths passed to
Qt's file system engine. When initializing the deployment tool for VS
projects we accidentally passed a file path containing '\0'. Fix that by
using an infix QString, not QChar.
Change-Id: Ieae066d20ac290354febd420abce68f28649b365
Reviewed-by: Andy Shaw <andy.shaw@qt.io>