If either the initial calloc or the xi2mask_new fails, grab is NULL,
but if a src grab is passed in, it was always being written to by
CopyGrab (and if that failed, dereferenced again in teardown).
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>