Fix use of uninitialized memory in ostree_builtin_checksum()

https://bugzilla.gnome.org/show_bug.cgi?id=705968

src/ostree/ot-builtin-checksum.c

@@ -26,6 +26,8 @@
 #include "ostree.h"
 #include "libgsystem.h"
 
+#include <string.h>
+
 static GOptionEntry options[] = {
   { NULL }
 };
@@ -61,6 +63,8 @@ ostree_builtin_checksum (int argc, char **argv, GFile *repo_path_path, GCancella
   gs_unref_object GFile *f = NULL;
   AsyncChecksumData data;
 
+  memset (&data, 0, sizeof (data));
+
   context = g_option_context_new ("FILENAME - Checksum a file or directory");
   g_option_context_add_main_entries (context, options, NULL);