xkb: Initialize 'bad' Atom in _XkbSetNamesCheck

When _XkbCheckAtoms returns NULL for an error, it always sets the
error return code, but GCC can't figure that out, so just initialize
the local variable, 'bad', in _XkbSetNamesCheck to eliminate the warning.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

xkb/xkb.c

@@ -3986,7 +3986,7 @@ _XkbSetNamesCheck(ClientPtr client, DeviceIntPtr dev,
 {
     XkbDescRec *xkb;
     CARD32 *tmp;
-    Atom bad;
+    Atom bad = None;
 
     tmp = data;
     xkb = dev->key->xkbInfo->desc;