downstream report: 
https://bugzilla.redhat.com/show_bug.cgi?id=695132

Start of backtrace: 

Core was generated by `xfce4-panel --display :0.0 --sm-client-id 2f4efd012-f282-4f92-8c11-aecca4357e38'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007fe15713fa4e in xfce_tasklist_button_enter_notify_event (button=0x21aa610 [GtkImageMenuItem], event=<optimized out>, child=0x1f70c80) at tasklist-widget.c:2508
2508	tasklist-widget.c: No such file or directory.
	in tasklist-widget.c

Thread 2 (Thread 0x7fe156f27700 (LWP 32320)):
#0  0x0000003a0e60e60d in read () at ../sysdeps/unix/syscall-template.S:82
No locals.
#1  0x0000003a11644a0b in read (__nbytes=20, __buf=0x7fe156f26bd0, __fd=<optimized out>) at /usr/include/bits/unistd.h:45
No locals.
#2  child_watch_helper_thread (data=<optimized out>) at gmain.c:4302
        b = "B", '\000' <repeats 18 times>
        list = <optimized out>
#3  0x0000003a116686d4 in g_thread_create_proxy (data=0x1db9960) at gthread.c:1897
        thread = 0x1db9960
        __PRETTY_FUNCTION__ = "g_thread_create_proxy"
#4  0x0000003a0e607d0b in start_thread (arg=0x7fe156f27700) at pthread_create.c:301
        __res = <optimized out>
        pd = 0x7fe156f27700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, -4921342416579968875, 140733893297104, 140605803100608, 0, 3, 4931807460254040213, -4915681306247806827}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = 0
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#5  0x0000003a0e2dfb7d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115
No locals.

Thread 1 (Thread 0x7fe15deca9a0 (LWP 32304)):
#0  0x00007fe15713fa4e in xfce_tasklist_button_enter_notify_event (button=0x21aa610 [GtkImageMenuItem], event=<optimized out>, child=0x1f70c80) at tasklist-widget.c:2508
        __inst = 0x4099b658
        __t = 31514080
        __r = <optimized out>
        _g_boolean_var_ = <optimized out>
        __PRETTY_FUNCTION__ = "xfce_tasklist_button_enter_notify_event"