[Reg 4.8->4.9] Crash in QmakeProjectManager::QmakeProject::collectData when opening a project

I have a project that opens successfully in Qt Creator 4.8.1, but in 4.9.0-beta1 and 4.9.0-beta2, Qt Creator consistently crashes while opening it.

Steps to reproduce:

• Delete ~/.config/QtProject
• git clone https://github.com/vuo/vuo.git
• Open vuo.pro in Qt Creator 4.9.0-beta1 or 4.9.0-beta2, and configure the project
• Wait a few seconds, and Qt Creator crashes

Crash report attached.