From 9ecac14aee50ab608159afff5878f6be782f5c74 Mon Sep 17 00:00:00 2001
From: Anna Shaleva <shaleva.ann@nspcc.ru>
Date: Thu, 30 Apr 2020 19:19:31 +0300
Subject: [PATCH] vm: fix bug in GetContextScriptHash()

v.Istack.Peek(n) can return nil pointer, so .Value() on this pointer
leads to panic here. Fixed by adding nil check.
---
 pkg/vm/context.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pkg/vm/context.go b/pkg/vm/context.go
index 4d1b9c00e..14b039dfd 100644
--- a/pkg/vm/context.go
+++ b/pkg/vm/context.go
@@ -226,7 +226,11 @@ func (c *Context) String() string {
 // GetContextScriptHash returns script hash of the invocation stack element
 // number n.
 func (v *VM) GetContextScriptHash(n int) util.Uint160 {
-	ctxIface := v.Istack().Peek(n).Value()
+	element := v.Istack().Peek(n)
+	if element == nil {
+		return util.Uint160{}
+	}
+	ctxIface := element.Value()
 	ctx := ctxIface.(*Context)
 	return ctx.ScriptHash()
 }