vnc: fix crash when no console attached

Since commit e99441a ("ui/curses: Do not use console_select()")
qemu_text_console_put_keysym() no longer checks for NULL console
argument, which leads to a later crash:

Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
0x00005555559ee186 in qemu_text_console_handle_keysym (s=0x0, keysym=31) at ../ui/console-vc.c:332
332	        } else if (s->echo && (keysym == '\r' || keysym == '\n')) {
(gdb) bt
 #0  0x00005555559ee186 in qemu_text_console_handle_keysym (s=0x0, keysym=31) at ../ui/console-vc.c:332
 #1  0x00005555559e18e5 in qemu_text_console_put_keysym (s=<optimized out>, keysym=<optimized out>) at ../ui/console.c:303
 #2  0x00005555559f2e88 in do_key_event (vs=vs@entry=0x5555579045c0, down=down@entry=1, keycode=keycode@entry=60, sym=sym@entry=65471) at ../ui/vnc.c:2034
 #3  0x00005555559f845c in ext_key_event (vs=0x5555579045c0, down=1, sym=65471, keycode=<optimized out>) at ../ui/vnc.c:2070
 qemu#4  protocol_client_msg (vs=0x5555579045c0, data=<optimized out>, len=<optimized out>) at ../ui/vnc.c:2514
 qemu#5  0x00005555559f515c in vnc_client_read (vs=0x5555579045c0) at ../ui/vnc.c:1607

Fixes: e99441a ("ui/curses: Do not use console_select()")
Fixes: https://issues.redhat.com/browse/RHEL-50529
Cc: qemu-stable@nongnu.org
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(cherry picked from commit 0e60fc8)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

Author: elmarco

ui/vnc.c

@@ -1935,7 +1935,7 @@ static void do_key_event(VncState *vs, int down, int keycode, int sym)
     }
 
     qkbd_state_key_event(vs->vd->kbd, qcode, down);
-    if (!qemu_console_is_graphic(vs->vd->dcl.con)) {
+    if (QEMU_IS_TEXT_CONSOLE(vs->vd->dcl.con)) {
         QemuTextConsole *con = QEMU_TEXT_CONSOLE(vs->vd->dcl.con);
         bool numlock = qkbd_state_modifier_get(vs->vd->kbd, QKBD_MOD_NUMLOCK);
         bool control = qkbd_state_modifier_get(vs->vd->kbd, QKBD_MOD_CTRL);