Description of problem:
When adding an account to gnome-online-accounts, it crashes.

Version-Release number of selected component (if applicable):
3.10.2-1.mga4.src.rpm

How reproducible:
Always

Steps to Reproduce:
1. Open the gnome-control-center
2. Click Online Accounts
3. Click the + button (to add an account)

(gdb) run
Starting program: /usr/bin/gnome-control-center 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Traceback (most recent call last):
  File "/usr/share/gdb/auto-load/usr/lib64/libgobject-2.0.so.0.3800.2-gdb.py", line 9, in <module>
    from gobject import register
  File "/usr/share/glib-2.0/gdb/gobject.py", line 3, in <module>
    import gdb.backtrace
ImportError: No module named backtrace
[New Thread 0x7fffdae66700 (LWP 606)]
[New Thread 0x7fffd88ca700 (LWP 632)]
[New Thread 0x7fffc884e700 (LWP 635)]

(gnome-control-center:581): GoaBackend-CRITICAL **: goa_provider_get_provider_features: assertion 'GOA_PROVIDER_GET_CLASS (provider)->get_provider_features != NULL' failed

(gnome-control-center:581): GoaBackend-CRITICAL **: goa_provider_get_provider_features: assertion 'GOA_PROVIDER_GET_CLASS (provider)->get_provider_features != NULL' failed

(gnome-control-center:581): GoaBackend-CRITICAL **: goa_provider_get_provider_features: assertion 'GOA_PROVIDER_GET_CLASS (provider)->get_provider_features != NULL' failed

(gnome-control-center:581): GoaBackend-CRITICAL **: goa_provider_get_provider_features: assertion 'GOA_PROVIDER_GET_CLASS (provider)->get_provider_features != NULL' failed

(gnome-control-center:581): GoaBackend-CRITICAL **: goa_provider_get_provider_features: assertion 'GOA_PROVIDER_GET_CLASS (provider)->get_provider_features != NULL' failed

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) thread all apply bt
No symbol "all" in current context.
(gdb) thread apply all bt

Thread 4 (Thread 0x7fffc884e700 (LWP 635)):
#0  0x00007fffefa4ae1d in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007ffff5b4cc71 in poll (__timeout=-1, __nfds=2, __fds=0x7fffc40049d0) at /usr/include/bits/poll2.h:46
#2  poll_func (ufds=0x7fffc40049d0, nfds=2, timeout=-1, userdata=0xb6efd0) at pulse/thread-mainloop.c:71
#3  0x00007ffff5b3e49c in pa_mainloop_poll (m=m@entry=0xbd5200) at pulse/mainloop.c:849
#4  0x00007ffff5b3eb0e in pa_mainloop_iterate (m=m@entry=0xbd5200, block=block@entry=1, retval=retval@entry=0x0) at pulse/mainloop.c:931
#5  0x00007ffff5b3ebc0 in pa_mainloop_run (m=0xbd5200, retval=retval@entry=0x0) at pulse/mainloop.c:949
#6  0x00007ffff5b4cc23 in thread (userdata=0xbdb620) at pulse/thread-mainloop.c:90
#7  0x00007fffe9fe8518 in internal_thread_func (userdata=0x10f6c00) at pulsecore/thread-posix.c:83
#8  0x00007ffff37fafab in start_thread (arg=0x7fffc884e700) at pthread_create.c:309
#9  0x00007fffefa555ad in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 3 (Thread 0x7fffd88ca700 (LWP 632)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fffd92e5c13 in pipe_semaphore_wait (sema=0xbb6a60) at ../../../../../src/gallium/auxiliary/os/os_thread.h:434
#2  radeon_drm_cs_emit_ioctl (param=0xbb6840) at radeon_drm_winsys.c:562
#3  0x00007ffff37fafab in start_thread (arg=0x7fffd88ca700) at pthread_create.c:309
#4  0x00007fffefa555ad in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 2 (Thread 0x7fffdae66700 (LWP 606)):
#0  0x00007fffefa4ae1d in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007ffff0066434 in g_main_context_poll (priority=2147483647, n_fds=3, fds=0x7fffd40010c0, timeout=-1, context=0x9a11f0) at gmain.c:4007
#2  g_main_context_iterate (context=0x9a11f0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3708
#3  0x00007ffff006689a in g_main_loop_run (loop=0x9a1180) at gmain.c:3907
#4  0x00007ffff06399b6 in gdbus_shared_thread_func (user_data=0x9a11c0) at gdbusprivate.c:278
#5  0x00007ffff008ae65 in g_thread_proxy (data=0x9a2850) at gthread.c:798
#6  0x00007ffff37fafab in start_thread (arg=0x7fffdae66700) at pthread_create.c:309
#7  0x00007fffefa555ad in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7ffff7f8f940 (LWP 581)):
#0  0x0000000000000000 in ?? ()
#1  0x00000000004805e0 in goa_panel_add_account_dialog_add_provider (add_account=<optimized out>, provider=0xf17250) at cc-online-accounts-add-account-dialog.c:440
#2  0x000000000047e71c in get_all_providers_cb (source=<optimized out>, res=<optimized out>, user_data=0xba2940) at cc-online-accounts-panel.c:706
#3  0x00007ffff05db8b7 in g_simple_async_result_complete (simple=0x11abb40) at gsimpleasyncresult.c:777
#4  0x00007ffff05db919 in complete_in_idle_cb (data=<optimized out>) at gsimpleasyncresult.c:789
#5  0x00007ffff0066146 in g_main_dispatch (context=0x9961a0) at gmain.c:3066
#6  g_main_context_dispatch (context=context@entry=0x9961a0) at gmain.c:3642
#7  0x00007ffff0066498 in g_main_context_iterate (context=context@entry=0x9961a0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3713
#8  0x00007ffff006653c in g_main_context_iteration (context=0x9961a0, context@entry=0x0, may_block=may_block@entry=1) at gmain.c:3774
#9  0x00007ffff06078dc in g_application_run (application=0x992100, argc=argc@entry=1, argv=argv@entry=0x7fffffffe5d8) at gapplication.c:1635
#10 0x000000000044a1a5 in main (argc=1, argv=0x7fffffffe5d8) at main.c:49


Reproducible: 

Steps to Reproduce: