segfault in in gcal_manager_get_default_source()

Those reports started with 3.26 in Ubuntu and are still happening in 3.32.2 https://bugs.launchpad.net/ubuntu/+source/gnome-calendar/+bug/1725005 reported also on fedora, e.g https://bugzilla.redhat.com/show_bug.cgi?id=1680240

The descriptions seem to suggest users hit the segfault when adding events to calendars

Backtrace from 3.30.1

#0  0x000055bf8ef92e1a in GCAL_IS_MANAGER (ptr=0x55bf933af2e0) at ../src/gcal-manager.h:32
        __inst = 0x55bf933af2e0
        __t = 94281255425088
        __r = <optimized out>
#1  gcal_manager_get_default_source (self=0x55bf933af2e0) at ../src/gcal-manager.c:1065
        _g_boolean_var_ = <optimized out>
        __func__ = "gcal_manager_get_default_source"
#2  0x000055bf8ef96407 in update_default_calendar_row (self=0x55bf9281e1e0) at ../src/gcal-quick-add-popover.c:487
        row = <optimized out>
        default_source = <optimized out>
#3  0x00007f88e4c1b3dd in g_closure_invoke (closure=0x55bf9326be60, return_value=0x0, n_param_values=2, param_values=0x7ffccc8df5f0, invocation_hint=0x7ffccc8df570) at gclosure.c:810
        marshal = 0x7f88e4c1e520 <g_cclosure_marshal_VOID__PARAM>
        marshal_data = 0x0
        in_marshal = 0
        real_closure = 0x55bf9326be40
        __func__ = "g_closure_invoke"
#4  0x00007f88e4c2e983 in signal_emit_unlocked_R (node=node@entry=0x55bf90bcae10, detail=detail@entry=203, instance=instance@entry=0x55bf90be0920, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffccc8df5f0) at gsignal.c:3635
        tmp = <optimized out>
        handler = 0x55bf9326a240
        accumulator = 0x0
        emission = {next = 0x7ffccc8dfbe0, instance = 0x55bf90be0920, ihint = {signal_id = 1, detail = 203, run_type = G_SIGNAL_RUN_FIRST}, state = EMISSION_RUN, chain_type = 4}
        class_closure = 0x55bf90bcad80
        hlist = <optimized out>
        handler_list = 0x55bf9326a240
        return_accu = 0x0
        accu = {g_type = 0, data = {{v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer = 0x0}}}
        signal_id = 1
        max_sequential_handler_number = 35412
        return_value_altered = 1
#5  0x00007f88e4c37aaa in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffccc8df7d0) at gsignal.c:3391
        instance_and_params = 0x7ffccc8df5f0
        signal_return_type = <optimized out>
        param_values = 0x7ffccc8df608
        node = <optimized out>
        i = <optimized out>
        n_params = <optimized out>
        __func__ = "g_signal_emit_valist"
#6  0x00007f88e4c380a3 in g_signal_emit (instance=instance@entry=0x55bf90be0920, signal_id=<optimized out>, detail=<optimized out>) at gsignal.c:3447
        var_args = {{gp_offset = 32, fp_offset = 48, overflow_arg_area = 0x7ffccc8df8b0, reg_save_area = 0x7ffccc8df7f0}}
#7  0x00007f88e4c1fe54 in g_object_dispatch_properties_changed (object=0x55bf90be0920, n_pspecs=<optimized out>, pspecs=<optimized out>) at gobject.c:1088
        i = <optimized out>