Allow NULL parameter in alpm_trans_commit

Fixes FS#7380: alpm crashes on passing NULL to alpm_trans_commit in
a sync operation.  Adds check that data parameter is not NULL in
several functions.

Signed-off-by: Allan McRae <mcrae_allan@hotmail.com>
[Dan: fix whitespace]
Signed-off-by: Dan McGee <dan@archlinux.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/libalpm/trans.c b/lib/libalpm/trans.c
index 582c76b7..292c7160 100644
--- a/lib/libalpm/trans.c
+++ b/lib/libalpm/trans.c
@@ -342,7 +342,9 @@ int _alpm_trans_addtarget(pmtrans_t *trans, char *target)
 
 int _alpm_trans_prepare(pmtrans_t *trans, alpm_list_t **data)
 {
-	*data = NULL;
+	if(data) {
+		*data = NULL;
+	}
 
 	ALPM_LOG_FUNC;