Check strdup for NULL return value.

_xcb_open does not check strdup's return value for NULL if launchd suport
was configured.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Signed-off-by: Uli Schlachter <psychon@znc.in>

src/xcb_util.c

@@ -265,6 +265,8 @@ static int _xcb_open(const char *host, char *protocol, const int display)
     struct stat sbuf;
     if (0 == stat(host, &sbuf)) {
         file = strdup(host);
+        if(file == NULL)
+            return -1;
         filelen = actual_filelen = strlen(file);
     } else
 #endif