Bug 27118

Steps to reproduce:

- start parcellite;
- select any text (e.g. with mouse from terminal window)
- call history with hotkey (menu is shown)
- using keyboard up and down arrows select menu item with previously selected text
- press enter

The program fails with segmentation fault. Output from gdb with debuginfo installed:

Program received signal SIGSEGV, Segmentation fault.
set_clipboard_text (h=0x610980, element=0x0) at main.c:1030
1030			gtk_clipboard_set_text(clipboard, element->data, -1);
1: element = (GSList *) 0x0
(gdb) bt
#0  set_clipboard_text (h=0x610980, element=0x0) at main.c:1030
#1  0x00000032cbc0f944 in g_closure_invoke (closure=0x77cf30, return_value=0x0, n_param_values=1, param_values=0x7b12c0, invocation_hint=<value optimized out>)
    at gclosure.c:774
#2  0x00000032cbc22458 in signal_emit_unlocked_R (node=<value optimized out>, detail=0, instance=0x7725b0, emission_return=0x0, instance_and_params=0x7b12c0)
    at gsignal.c:3272
#3  0x00000032cbc2bb75 in g_signal_emit_valist (instance=<value optimized out>, signal_id=<value optimized out>, detail=<value optimized out>, 
    var_args=<value optimized out>) at gsignal.c:3003
#4  0x00000032cbc2bd03 in g_signal_emit (instance=<value optimized out>, signal_id=<value optimized out>, detail=<value optimized out>) at gsignal.c:3060
#5  0x00000032cea63806 in IA__gtk_widget_activate (widget=0x7725b0) at gtkwidget.c:5023
#6  0x00000032ce9570cd in IA__gtk_menu_shell_activate_item (menu_shell=0x6657a0, menu_item=0x7725b0, force_deactivate=<value optimized out>)
    at gtkmenushell.c:1256
#7  0x00000032cbc0f944 in g_closure_invoke (closure=0x6a53b0, return_value=0x7fffffffd410, n_param_values=2, param_values=0x75eb60, 
    invocation_hint=<value optimized out>) at gclosure.c:774
#8  0x00000032cbc22286 in signal_emit_unlocked_R (node=<value optimized out>, detail=0, instance=0x6657a0, emission_return=0x7fffffffd410, 
    instance_and_params=0x75eb60) at gsignal.c:3310
#9  0x00000032cbc2b177 in g_signal_emitv (instance_and_params=<value optimized out>, signal_id=<value optimized out>, detail=0, return_value=0x7fffffffd410)
    at gsignal.c:2907
#10 0x00000032ce88ae1e in gtk_binding_entry_activate (entry=<value optimized out>, object=<value optimized out>) at gtkbindings.c:537
#11 0x00000032ce88b378 in binding_match_activate (pspec_list=<value optimized out>, object=0x6657a0, path_length=12, path=0x6eabe0 "GtkMenuShell", 
    path_reversed=0x6a9c70 "llehSuneMktG", unbound=0x7fffffffd4f8) at gtkbindings.c:1124
#12 0x00000032ce88b612 in gtk_bindings_activate_list (object=0x6657a0, entries=<value optimized out>, is_release=<value optimized out>) at gtkbindings.c:1269
#13 0x00000032ce88c592 in IA__gtk_bindings_activate_event (object=0x6657a0, event=0x73af30) at gtkbindings.c:1364
#14 0x00000032ce955f98 in gtk_menu_shell_key_press (widget=0x6657a0, event=0x73af30) at gtkmenushell.c:869
#15 0x00000032ce94c8ea in gtk_menu_key_press (widget=0x6657a0, event=0x73af30) at gtkmenu.c:3105
#16 0x00000032ce9435a8 in _gtk_marshal_BOOLEAN__BOXED (closure=0x65a500, return_value=0x7fffffffd810, n_param_values=<value optimized out>, 
    param_values=0x6cfd90, invocation_hint=<value optimized out>, marshal_data=<value optimized out>) at gtkmarshalers.c:86
#17 0x00000032cbc0f944 in g_closure_invoke (closure=0x65a500, return_value=0x7fffffffd810, n_param_values=2, param_values=0x6cfd90, 
    invocation_hint=<value optimized out>) at gclosure.c:774
#18 0x00000032cbc22286 in signal_emit_unlocked_R (node=<value optimized out>, detail=0, instance=0x6657a0, emission_return=0x7fffffffd980, 
    instance_and_params=0x6cfd90) at gsignal.c:3310
#19 0x00000032cbc2b93d in g_signal_emit_valist (instance=<value optimized out>, signal_id=<value optimized out>, detail=<value optimized out>, 
    var_args=<value optimized out>) at gsignal.c:3013
#20 0x00000032cbc2bd03 in g_signal_emit (instance=<value optimized out>, signal_id=<value optimized out>, detail=<value optimized out>) at gsignal.c:3060
#21 0x00000032cea6469f in gtk_widget_event_internal (widget=0x6657a0, event=0x73af30) at gtkwidget.c:4992
#22 0x00000032ce941786 in IA__gtk_propagate_event (widget=0x6657a0, event=0x73af30) at gtkmain.c:2455
#23 0x00000032ce941a8b in IA__gtk_main_do_event (event=0x73af30) at gtkmain.c:1684
#24 0x00000032ce45ee2c in gdk_event_dispatch (source=<value optimized out>, callback=<value optimized out>, user_data=<value optimized out>)
    at gdkevents-x11.c:2377
#25 0x00000032cb449c9b in g_main_dispatch (context=0x64b250) at gmain.c:2441
#26 g_main_context_dispatch (context=0x64b250) at gmain.c:3011
#27 0x00000032cb44a4d8 in g_main_context_iterate (context=0x64b250, block=1, dispatch=1, self=<value optimized out>) at gmain.c:3089
#28 0x00000032cb44aa52 in g_main_loop_run (loop=0x648210) at gmain.c:3297
#29 0x00000032ce940a87 in IA__gtk_main () at gtkmain.c:1256
#30 0x00000000004086ea in main (argc=1, argv=0x7fffffffde38) at main.c:1499