xfreerdp crashes on RDP server redirection when clipboard redirection is enabled

[p-pautov]

This is FreeRDP version 2.0.0-dev3 (7eb12bb).

(gdb) bt
#0  0x00007fad0ba97428 in __GI_raise (sig=11) at ../sysdeps/unix/sysv/linux/raise.c:54
#1  0x00007fad0c67db30 in fatal_handler (signum=11)
    at ../FreeRDP/libfreerdp/utils/signal.c:67
#2  <signal handler called>
#3  0x0000000000418594 in xf_cliprdr_init (xfc=0x19bf670, cliprdr=0x7facfc000a30)
    at ../FreeRDP/client/X11/xf_cliprdr.c:1757
#4  0x00000000004139a9 in xf_OnChannelConnectedEventHandler (context=0x19bf670, e=0x7fad00fd2870)
    at ../FreeRDP/client/X11/xf_channels.c:63
#5  0x00007fad0be81a48 in PubSub_OnEvent (pubSub=0x19c01d0, EventName=0x7fad0c7d4c00 "ChannelConnected",
    context=0x19bf670, e=0x7fad00fd2870)
    at ../FreeRDP/winpr/libwinpr/utils/collections/PubSub.c:188
#6  0x00007fad0c6e99c5 in PubSub_OnChannelConnected (pubSub=0x19c01d0, context=0x19bf670, e=0x7fad00fd2870)
    at ../FreeRDP/include/freerdp/event.h:84
#7  0x00007fad0c6ea7df in freerdp_channels_post_connect (channels=0x19f85c0, instance=0x19bf3e0)
    at ../FreeRDP/libfreerdp/core/client.c:380
#8  0x00007fad0c6fa1c8 in rdp_client_redirect (rdp=0x19c4a90)
    at ../FreeRDP/libfreerdp/core/connection.c:423
#9  0x00007fad0c706cca in rdp_check_fds (rdp=0x19c4a90)
    at ../FreeRDP/libfreerdp/core/rdp.c:1514
#10 0x00007fad0c6f9dba in rdp_client_connect (rdp=0x19c4a90)
    at ../FreeRDP/libfreerdp/core/connection.c:305
#11 0x00007fad0c6e7569 in freerdp_connect (instance=0x19bf3e0)
    at ../FreeRDP/libfreerdp/core/freerdp.c:189
#12 0x0000000000427032 in xf_client_thread (param=0x19bf3e0)
    at ../FreeRDP/client/X11/xf_client.c:1485
#13 0x00007fad0beb368e in thread_launcher (arg=0x1a0a560)
    at ../FreeRDP/winpr/libwinpr/thread/thread.c:319
#14 0x00007fad0b4266ba in start_thread (arg=0x7fad00fd3700) at pthread_create.c:333
#15 0x00007fad0bb6941d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Basically, in case of RDP server redirection xf_cliprdr_init() is called before xf_clipboard_new(), which causes NULL deference.