winex11: Fix printing NULL strings.

[Francois Gouget]

---

This fixes a crash that occurred in the conformance tests on my Solaris 
VMs when tracing was turned on.

 dlls/winex11.drv/keyboard.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/dlls/winex11.drv/keyboard.c b/dlls/winex11.drv/keyboard.c
index 423921a..47317e6 100644
--- a/dlls/winex11.drv/keyboard.c
+++ b/dlls/winex11.drv/keyboard.c
@@ -2301,7 +2301,7 @@ INT CDECL X11DRV_GetKeyNameText(LONG lParam, LPWSTR lpBuffer, INT nSize)
       name = XKeysymToString(keys);
       wine_tsx11_unlock();
       TRACE("found scan=%04x keyc=%u keysym=%04x string=%s\n",
-            scanCode, keyc, (int)keys, name);
+            scanCode, keyc, (int)keys, debugstr_a(name));
       if (lpBuffer && nSize && name)
           return MultiByteToWideChar(CP_UNIXCP, 0, name, -1, lpBuffer, nSize);
   }
-- 
1.7.5.4