OpenWrt shutdown ModemManager/libglib crash

[Peter Naulls]

When rebooting in OpenWrt:

[  548.410590] mtk_soc_eth 1e100000.ethernet eth0: Link is Down
[  548.425055] device eth0 left promiscuous mode
[  548.434058] br-lan: port 1(eth0) entered disabled state
[  550.455000] do_page_fault(): sending SIGSEGV to ModemManager for invalid read 
access from 00000000
[  550.472911] epc = 77c4717d in libglib-2.0.so.0.7000.4[77c10000+df000]
[  550.485799] ra  = 5566f85f in ModemManager[55630000+183000]
[  553.460649] reboot: Restarting system

This is obviously an awkward point to debug anything, and it's perhaps not
super important at this point, but it's pretty repeatable and has happened
as long as I can remember.

This is with MM 1.20.0, glib 2.70.4 and libqmi 1.32.0.

Open to ideas on debugging here.