port-qmi: fix double free when WDA Set Data Format fails

Thread 0(id: 4915) CRASHED [ SIGABRT@0x0000000000000000 ]
  0x00007b0f6732fa3f (libc.so.6 - pthread_kill.c: 44) __pthread_kill_implementation
  0x00007b0f672e4c6c (libc.so.6 - raise.c: 26) raise
  0x00007b0f672d0462 (libc.so.6 - abort.c: 79) abort
  0x00007b0f67323347 (libc.so.6 - libc_fatal.c: 155) __libc_message
  0x00007b0f67339929 (libc.so.6 - malloc.c: 5664) malloc_printerr
  0x00007b0f6733b5cb (libc.so.6 - malloc.c: 4439) _int_free
  0x00007b0f6733e279 (libc.so.6 - malloc.c: 3391) __libc_free
  0x00007b0f67abcabe (libglib-2.0.so.0 - gerror.c: 856) g_error_free
  0x000059fc4262623e (ModemManager - glib-autocleanups.h: 54) glib_autoptr_clear_GError
  0x000059fc4262623e (ModemManager - glib-autocleanups.h: 54) glib_autoptr_cleanup_GError
  0x000059fc4262623e (ModemManager - mm-port-qmi.c: 1501) set_data_format_ready
  0x00007b0f67985e57 (libgio-2.0.so.0 - gtask.c: 1309) g_task_return_now
  0x00007b0f67984e21 (libgio-2.0.so.0 - gtask.c: 1378) g_task_return
  0x00007b0f677f7107 (libqmi-glib.so.5 - qmi-wda.c: 4761) set_data_format_ready
  0x00007b0f67972329 (libgio-2.0.so.0 - gsimpleasyncresult.c: 804) g_simple_async_result_complete
  0x00007b0f6797240a (libgio-2.0.so.0 - gsimpleasyncresult.c: 816) complete_in_idle_cb
  0x00007b0f67ad17a4 (libglib-2.0.so.0 - gmain.c: 3460) g_main_dispatch
  0x00007b0f67ad17a4 (libglib-2.0.so.0 - gmain.c: 4200) g_main_context_dispatch
  0x00007b0f67ad1ac3 (libglib-2.0.so.0 - gmain.c: 4276) g_main_context_iterate
  0x00007b0f67ad1d41 (libglib-2.0.so.0 - gmain.c: 4479) g_main_loop_run
  0x000059fc425657df (ModemManager - main.c: 236) main
  0x00007b0f672d06c5 (libc.so.6 - libc_start_call_main.h: 58) __libc_start_call_main
  0x00007b0f672d0781 (libc.so.6 - libc-start.c: 389) __libc_start_main_impl
  0x000059fc42565130 (ModemManager) _start
  0x00007fffdea098c7