broadband-modem: exit with error if enable() while in unknown state
We should not assert if the modem is flagged as invalid but an outstanding enabling request is processed. Let's exit gracefully and let the object get properly disposed afterwards.
(libc.so.6 - pthread_kill.c: 44) __pthread_kill_implementation
(libc.so.6 - raise.c: 26) raise
(libc.so.6 - abort.c: 79) abort
(libglib-2.0.so.0 - gtestutils.c: 3450) g_assertion_message
(libglib-2.0.so.0 - gtestutils.c: 3476) g_assertion_message_expr
(ModemManager - mm-broadband-modem.c) enable
(ModemManager - mm-iface-modem.c: 2340) handle_enable_auth_ready
(libgio-2.0.so.0 - gtask.c: 1309) g_task_return_now
(libgio-2.0.so.0 - gtask.c: 1378) g_task_return
(ModemManager - mm-base-modem.c: 2011) lock_after_authorize_ready
(libgio-2.0.so.0 - gtask.c: 1309) g_task_return_now
(libgio-2.0.so.0 - gtask.c: 1378) g_task_return
(ModemManager - mm-base-modem.c: 1841) base_modem_operation_run
(ModemManager - mm-base-modem.c: 764) state_operation_ready
(libgio-2.0.so.0 - gtask.c: 1309) g_task_return_now
(libgio-2.0.so.0 - gtask.c: 1323) complete_in_idle_cb
(libglib-2.0.so.0 - gmain.c: 3460) g_main_dispatch
(libglib-2.0.so.0 - gmain.c: 4200) g_main_context_dispatch
(libglib-2.0.so.0 - gmain.c: 4276) g_main_context_iterate
(libglib-2.0.so.0 - gmain.c: 4479) g_main_loop_run
(ModemManager - main.c: 236) main
(libc.so.6 - libc_start_call_main.h: 58) __libc_start_call_main
(libc.so.6 - libc-start.c: 360) __libc_start_main_impl
(ModemManager + 0x000b8850) _start