Error: "Must construct a QApplication before a QWidget"

[Lubomir I. Ivanov]

i've updated to Qt 5.9.0 today and after building Subsurface on
Windows i'm getting a:

QWidget: Must construct a QApplication before a QWidget
Invalid parameter passed to C runtime function.
Invalid parameter passed to C runtime function.

and the app terminates with:
"This application has requested the Runtime to terminate it in an unusual way."

the above error cannot be debugged properly most of the time (e.g. asserts).

https://stackoverflow.com/questions/23804238/debugging-qwidget-must-construct-a-qapplication-before-a-qwidget-invalid-par

according the comments in the thread we are probably creating a widget
in a header somewhere before the QApplication instance in created.

i'm trying to hunt what widget / header is causing that.

lubomir
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