FileDialog hangs on startup on Windows, with offline drives

If I use a QML FileDialog in my app, running on Win7, and one or more of the network computers that are referred to by mapped drive letters are sleeping, the program can take 30 seconds to two minutes before the main window appears.

This was reported as QTBUG-57832, but in 2.5 years, nothing seems to have been done about it, and it's a killer issue for me. In that bug report, it was suggested that the problem lies with the Qt or QML dialog box that is created as a backup mechanism if the system dialog box is "not available". But it's always available, so it has no business creating these extra objects, especially when doing so hangs on a needless network access.

If this can't be fixed cleanly, at least provide a property that can disable the unnecessary object creation that causes this problem. In the absence of that, the only solution I can figure out is to ditch FileDialog, and write my own object from scratch, but that's a lot of work.