[PATCH 3/5] config: add BUG() statement instead of possible segfault

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

The git_die_config() method calls git_config_get_value_multi() but
immediately navigates to its first value without checking if the result
is NULL or empty. Callers should only call git_die_config() if there is
at least one value for the given 'key', but such a mistaken use might
slip through. It would be better to show a BUG() statement than a
possible segfault.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 config.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/config.c b/config.c
index bf89afbdab0..0c41606c7d4 100644
--- a/config.c
+++ b/config.c
@@ -2833,8 +2833,13 @@ void git_die_config(const char *key, const char *err, ...)
 		va_end(params);
 	}
 	values = git_config_get_value_multi(key);
-	kv_info = values->items[values->nr - 1].util;
-	git_die_config_linenr(key, kv_info->filename, kv_info->linenr);
+
+	if (values && values->nr) {
+		kv_info = values->items[values->nr - 1].util;
+		git_die_config_linenr(key, kv_info->filename, kv_info->linenr);
+	} else {
+		BUG("expected a non-empty list of values");
+	}
 }
 
 /*
-- 
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