compositor-fbdev: MAP_FAILED is not NULL

Fix the assumption that MAP_FAILED would be equal to NULL. It is not.
Set 'fb' explicitly to NULL on mmap failure so that comparisons to NULL
would produce the expected result.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Daniel Stone <daniels@collabora.com>
1 file changed