do not segfault if make_cache_entry failed

diff --git a/combine-diff.c b/combine-diff.c
index dcb90b1701aab6f2e22a0953067d85dcf734d6d2..de83c6972e9dffbd634e5cc09b5e455ec22c6c48 100644 (file)
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -683,9 +683,13 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
        int i, show_hunks;
        int working_tree_file = is_null_sha1(elem->sha1);
        int abbrev = DIFF_OPT_TST(opt, FULL_INDEX) ? 40 : DEFAULT_ABBREV;
+       const char *a_prefix, *b_prefix;
        mmfile_t result_file;
 
        context = opt->context;
+       a_prefix = opt->a_prefix ? opt->a_prefix : "a/";
+       b_prefix = opt->b_prefix ? opt->b_prefix : "b/";
+
        /* Read the result of merge first */
        if (!working_tree_file)
                result = grab_blob(elem->sha1, &result_size);
@@ -861,13 +865,13 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
                        dump_quoted_path("--- ", "", "/dev/null",
                                         c_meta, c_reset);
                else
-                       dump_quoted_path("--- ", opt->a_prefix, elem->path,
+                       dump_quoted_path("--- ", a_prefix, elem->path,
                                         c_meta, c_reset);
                if (deleted)
                        dump_quoted_path("+++ ", "", "/dev/null",
                                         c_meta, c_reset);
                else
-                       dump_quoted_path("+++ ", opt->b_prefix, elem->path,
+                       dump_quoted_path("+++ ", b_prefix, elem->path,
                                         c_meta, c_reset);
                dump_sline(sline, cnt, num_parent,
                           DIFF_OPT_TST(opt, COLOR_DIFF));