Bug 1687148

Description of problem:
Started a virtual machine (f30) on a f30 host.
Virt-viewer crashes when reaching graphical target.
I saw lightdm login manager just before the crash happens.
Same happens if i am using virt-manger to fire up the VM.
It happens with all VMs which i use.
All VMs are starting well under f28 or f29 host.
I am using a dualboot system with several fedora versions.

Version-Release number of selected component:
virt-viewer-7.0-2.fc30

Additional info:
reporter:       libreport-2.10.0
backtrace_rating: 4
cmdline:        remote-viewer spice://localhost:5900
crash_function: gst_caps_set_simple_valist
executable:     /usr/bin/remote-viewer
journald_cursor: s=1d4f5cc7a71e4384a44220d63b996328;i=83b38;b=e0e98ecacc1345f7a20ba6220dac867c;m=942aef0;t=583bb950349a4;x=ff3e0508a90e4a83
kernel:         5.0.0-300.fc30.x86_64
rootdir:        /
runlevel:       N 5
type:           CCpp
uid:            1000

Truncated backtrace:
Thread no. 1 (9 frames)
 #0 gst_caps_set_simple_valist at gstcaps.c:1082
 #1 gst_caps_set_simple at gstcaps.c:1115
 #2 gst_pulse_format_info_to_caps at pulseutil.c:495
 #3 gst_pulsesrc_create_stream at pulsesrc.c:1332
 #4 gst_pulsesrc_negotiate at pulsesrc.c:1451
 #5 gst_base_src_negotiate at gstbasesrc.c:3379
 #6 gst_base_src_loop at gstbasesrc.c:2801
 #7 gst_task_func at gsttask.c:328
 #9 g_thread_proxy at ../glib/gthread.c:805