Qt online installer and updated MaintenanceTool.app crash on OS X 10.9

I'm aware that Qt 5.9 dropped official support for Mac OS X 10.9, but has support for that and earlier OS versions been dropped completely?

I ran my existing copy of the MaintenanceTool.app (last updated for 5.9.0RC), which insisted on updating itself first. The new version crashes:

```

> /usr/local/qt/5/MaintenanceTool.app/Contents/MacOS/MaintenanceTool

2017-07-05 12:05:31.589 MaintenanceTool[45590:303] +[NSGraphicsContext graphicsContextWithCGContext:flipped:]: unrecognized selector sent to class 0x7fff764468f8

[0] Fatal: Unknown exception caught.

Unknown exception caught.

Abort

```

The current webinstaller also crashes immediately, for the same reason:

```

Jul 5 12:08:38 Portia.local qt-unified-mac-x64-3.0.0-online[45661]: +[NSGraphicsContext graphicsContextWithCGContext:flipped:]: unrecognized selector sent to class 0x7fff764468f8
Jul 5 12:08:39 Portia com.apple.launchd.peruser.505[280] ([0x0-0x78d78d].com.yourcompany.installerbase[45661]): Job appears to have crashed: Abort trap: 6
Jul 5 12:08:39 Portia.local ReportCrash[45664]: Saved crash report for qt-unified-mac-x64-3.0.0-online[45661] version 0 to /Users/bertin/Library/Logs/DiagnosticReports/qt-unified-mac-x64-3.0.0-online_2017-07-05-120839_Portia.crash

```

It'd be nice if users of older OS versions could still install the supported versions, and not just by downloading the 3.5Gb offline installer.