Watch for modem manager changes

I have tested it and I confirm it fixes the issue of seeing no SMS conversation when launching chatty. That is a big fix in term of UX! Thank you @mohammed.sadiq !

@francois.techene Out of curiosity - could you show the output of systemctl status ModemManager?

purism@pureos:~$ systemctl status ModemManager
● ModemManager.service - Modem Manager
   Loaded: loaded (/lib/systemd/system/ModemManager.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2020-07-10 11:02:16 CEST; 19min ago
 Main PID: 518 (ModemManager)
    Tasks: 5 (limit: 3112)
   Memory: 10.1M
   CGroup: /system.slice/ModemManager.service
           ├─518 /usr/sbin/ModemManager --filter-policy=strict
           └─654 /usr/lib/libqmi/qmi-proxy

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

mentioned in merge request chatty!419 (closed)

I can confirm that this works.

To test it:

stop ModemManager
start chatty
start ModemManager
???
Profit ! (sms chat history appears and new chat button is sensitive again)

Out of curiosity I tested the "reverse" by stopping ModemManager while chatty is running. This currently leads to a segmentation fault

(sm.puri.Chatty:3131): GLib-GObject-CRITICAL **: 21:46:25.539: g_object_unref: assertion 'G_IS_OBJECT (object)' failed

Thread 1 "chatty" received signal SIGSEGV, Segmentation fault.
__strptime_internal (rp=<optimized out>, fmt=0xffffe2331e1a "%m%d%H%M%S%z", tmp=0xffffffffe4b0, statep=0x0, locale=0xfffff6ce2378 <_nl_global_locale>) at strptime_l.c:754
754	strptime_l.c: No such file or directory.
(gdb) bt
#0  __strptime_internal (rp=<optimized out>, fmt=0xffffe2331e1a "%m%d%H%M%S%z", tmp=0xffffffffe4b0, statep=0x0, locale=0xfffff6ce2378 <_nl_global_locale>) at strptime_l.c:754
#1  0x0000ffffe232f74c in pur_mm_get_sms_properties (sms_props=0xaaaaaadcd460) at mm-sms.c:498
#2  0x0000ffffe232ef10 in cb_sms_state_change (sms=0xffffdc00c570, pspec=0xaaaaaabd4150, sms_props=0xaaaaaadcd460) at mm-sms.c:274
#3  0x0000fffff7d61bc4 in g_closure_invoke () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#4  0x0000fffff7d766fc in ?? () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#5  0x0000fffff7d80950 in g_signal_emit_valist () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#6  0x0000fffff7d81250 in g_signal_emit () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#7  0x0000fffff7d669b0 in ?? () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#8  0x0000fffff7d6908c in g_object_notify () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#9  0x0000ffffe22a2574 in ?? () from /lib/aarch64-linux-gnu/libmm-glib.so.0
#10 0x0000fffff7d61bc4 in g_closure_invoke () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#11 0x0000fffff7d75ee4 in ?? () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#12 0x0000fffff7d80950 in g_signal_emit_valist () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#13 0x0000fffff7d81250 in g_signal_emit () from /lib/aarch64-linux-gnu/libgobject-2.0.so.0
#14 0x0000fffff7ee9aac in ?? () from /lib/aarch64-linux-gnu/libgio-2.0.so.0
#15 0x0000fffff7ed6814 in ?? () from /lib/aarch64-linux-gnu/libgio-2.0.so.0
#16 0x0000fffff7c6435c in g_main_context_dispatch () from /lib/aarch64-linux-gnu/libglib-2.0.so.0
#17 0x0000fffff7c64708 in ?? () from /lib/aarch64-linux-gnu/libglib-2.0.so.0
#18 0x0000fffff7c647ac in g_main_context_iteration () from /lib/aarch64-linux-gnu/libglib-2.0.so.0
#19 0x0000fffff7eaddc4 in g_application_run () from /lib/aarch64-linux-gnu/libgio-2.0.so.0
#20 0x0000aaaaaaac0308 in main ()