nmcli: fix crash in nmc_connection_check_deprecated()
Summary
It's not clear in which circumstances, but 'type' can be NULL as in the following backtrace:
nmc_connection_check_deprecated (c=c@entry=0x55d93f937610) at src/nmcli/connections.c:676
connection_warnings (nmc=nmc@entry=0x55d93f5ae5e0 <nm_cli>, connection=connection@entry=0x55d93f937610) at src/nmcli/connections.c:5464
add_connection_cb (client=<optimized out>, result=<optimized out>, user_data=0x55d93fc83820) at src/nmcli/connections.c:5510
g_task_return_now (task=0x55d93fc86fd0 [GTask]) at ../gio/gtask.c:1361
g_task_return (type=<optimized out>, task=0x55d93fc86fd0 [GTask]) at ../gio/gtask.c:1430
g_task_return (task=0x55d93fc86fd0 [GTask], type=<optimized out>) at ../gio/gtask.c:1387
_request_wait_complete () at /lib64/libnm.so.0
_nm_client_notify_event_emit_parts () at /lib64/libnm.so.0
_dbus_handle_changes_commit () at /lib64/libnm.so.0
_nm_client_get_settings_call_cb () at /lib64/libnm.so.0
_nm_client_dbus_call_simple_cb () at /lib64/libnm.so.0
g_task_return_now (task=0x55d93f7bd6f0 [GTask]) at ../gio/gtask.c:1361
g_task_return (type=<optimized out>, task=0x55d93f7bd6f0 [GTask]) at ../gio/gtask.c:1430
g_task_return (task=0x55d93f7bd6f0 [GTask], type=<optimized out>) at ../gio/gtask.c:1387
g_dbus_connection_call_done (source=<optimized out>, result=<optimized out>, user_data=0x55d93f7bd6f0) at ../gio/gdbusconnection.c:5895
g_task_return_now (task=0x55d93f7bd7b0 [GTask]) at ../gio/gtask.c:1361
complete_in_idle_cb (task=task@entry=0x55d93f7bd7b0) at ../gio/gtask.c:1375
g_idle_dispatch (source=0x7f15b007c940, callback=0x7f15ca7e4850 <complete_in_idle_cb>, user_data=0x55d93f7bd7b0) at ../glib/gmain.c:6150
g_main_dispatch (context=0x55d93f77cde0) at ../glib/gmain.c:3344
g_main_context_dispatch_unlocked (context=0x55d93f77cde0) at ../glib/gmain.c:4152
g_main_context_iterate_unlocked.isra.0 (context=0x55d93f77cde0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4217
g_main_loop_run (loop=0x55d93f7589b0) at ../glib/gmain.c:4419
main (argc=19, argv=0x7fff77359138) at src/nmcli/nmcli.c:1044
Fixes: f377114d ('cli: connection: check for deprecated features')