PyQt5 seg fault when importing QQuickImageProvider - pyqt5

Question

i've encountered a very weird behavior which led to a seg fault when working on my app.
can someone please explain why it crashes ?
system:
ubuntu 18.04
PyQt 5.9.2
python 3.6
conditions:
have a QApplication based class
create QQmlApplicationEngine (even if its not used)
import- from PyQt5.QtQuick import QQuickImageProvider (even if its not used)
have a signal/slot that send/recieve a list type and send a [None]
emit the signal only after the engine is instantiated
** it doesnt matter if the slot has a #pyqtslot decorator or not
** if i change the signal signature to object instead of list everything is fine
** if you remove even one of the conditions you wont get the seg fault.
example:
import sys
from PyQt5.QtCore import QObject, pyqtSignal
from PyQt5.QtWidgets import QApplication
from PyQt5.QtQml import QQmlApplicationEngine
from PyQt5.QtQuick import QQuickImageProvider # if you comment out it wont crash
APP = None
class SomeCrashingClass(QObject):
sig = pyqtSignal(list)
def __init__(self):
QObject.__init__(self)
self.sig.connect(self.my_func)
self.sig.emit([None]) # if you send a [] it wont crash
def my_func(self):
print(f"-------------everything is fineeeeeeeeeeeeeeeeeeee-----------------")
class CrashingApp(QApplication):
def __init__(self):
super(CrashingApp, self).__init__(sys.argv)
self._engine = QQmlApplicationEngine() # if you comment out it wont crash
bla = SomeCrashingClass()
def run(self):
print(f"---------------------running the app ------------------")
exit_status = self.exec_()
print(f"----------exit status {exit_status}")
def run():
global APP
APP = CrashingApp()
sys.exit(APP.run())
if __name__ == "__main__":
run()
EDIT:
changing sig = pyqtSignal(object) solves the issue