diff: allow passing NULL to diff_free_filespec_data()

Commit 3aef54e8b8 ("diff: munmap() file contents before running external
diff") introduced calls to diff_free_filespec_data in
run_external_diff, which may pass NULL pointers.

Fix this and prevent any such bugs in the future by making
`diff_free_filespec_data(NULL)` a no-op.

Fixes: 3aef54e8b8 ("diff: munmap() file contents before running external diff")
Signed-off-by: Jinoh Kang <luke1337@theori.io>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/diff.c b/diff.c
index 2bb2f8f57e..ffdb08d5bf 100644
--- a/diff.c
+++ b/diff.c
@@ -4111,6 +4111,9 @@ void diff_free_filespec_blob(struct diff_filespec *s)
 
 void diff_free_filespec_data(struct diff_filespec *s)
 {
+	if (!s)
+		return;
+
 	diff_free_filespec_blob(s);
 	FREE_AND_NULL(s->cnt_data);
 }