Use the macro FREE_AND_NULL to release memory allocated for
'head_name' and clear its pointer.
Patch generated with 'contrib/coccinelle/free.cocci' and Coccinelle
v1.0.7 (previous Coccinelle versions don't notice this).
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>