From fd899481643feeed874c95060fa50cb75f9d993a Mon Sep 17 00:00:00 2001
From: dearblue <dearblue@users.noreply.github.com>
Date: Mon, 15 Jul 2019 11:23:50 +0900
Subject: Fix empty array refers; ref #4556

For example, `"".unpack("")` evaluates to `[]`.
---
 mrbgems/mruby-pack/src/pack.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mrbgems/mruby-pack/src/pack.c b/mrbgems/mruby-pack/src/pack.c
index 894c4555f..9f091194b 100644
--- a/mrbgems/mruby-pack/src/pack.c
+++ b/mrbgems/mruby-pack/src/pack.c
@@ -1299,7 +1299,12 @@ pack_unpack(mrb_state *mrb, mrb_value str, int single)
     if (single) break;
   }
 
-  if (single) return RARRAY_PTR(result)[0];
+  if (single) {
+    if (RARRAY_LEN(result) > 0) {
+      return RARRAY_PTR(result)[0];
+    }
+    return mrb_nil_value();
+  }
   return result;
 }
 
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