fix: npe when agent message has no receipts

Author: alanshaw

core/message/message.go

@@ -101,6 +101,9 @@ func (m *message) Receipt(root ipld.Link) (receipt.AnyReceipt, bool, error) {
 }
 
 func (m *message) Get(link ipld.Link) (ipld.Link, bool) {
+	if m.data.Report == nil {
+		return nil, false
+	}
 	var rcpt ipld.Link
 	found := false
 	for _, k := range m.data.Report.Keys {

core/message/message_test.go

@@ -21,6 +21,9 @@ func TestMessageReceipts(t *testing.T) {
 
 		rcpts := msg.Receipts()
 		require.Len(t, rcpts, 0)
+
+		_, ok := msg.Get(helpers.RandomCID())
+		require.False(t, ok)
 	})
 
 	t.Run("one receipt", func(t *testing.T) {