[FAB-12438] Fix NPE at deliverSupport.GetChain

FAB-12335 Dropped the boolean value, but a nil value
that is returned as an interface without an explicit
"return nil" is returned as a "nil interface type" pointer
and expressions such as "pt == nil" are evaluated to false,
which causes a NPE.

Change-Id: Ieaaa0e8731b6588eeab7f994fe3864c3bb9f7f4b
Signed-off-by: yacovm <yacovm@il.ibm.com>

orderer/common/server/server.go

@@ -39,7 +39,11 @@ type deliverSupport struct {
 }
 
 func (ds deliverSupport) GetChain(chainID string) deliver.Chain {
- return ds.Registrar.GetChain(chainID)
+ chain := ds.Registrar.GetChain(chainID)
+ if chain == nil {
+ return nil
+ }
+ return chain
 }
 
 type server struct {

orderer/common/server/server_test.go

@@ -20,6 +20,7 @@ import (
  ab "github.com/hyperledger/fabric/protos/orderer"
  "github.com/hyperledger/fabric/protos/utils"
 
+ "github.com/hyperledger/fabric/orderer/common/multichannel"
  "github.com/stretchr/testify/assert"
  "google.golang.org/grpc"
  "google.golang.org/grpc/peer"
@@ -149,3 +150,11 @@ func TestDeliverMsgTrace(t *testing.T) {
  }
  }, t)
 }
+
+func TestDeliverNoChannel(t *testing.T) {
+ r := &multichannel.Registrar{}
+ ds := &deliverSupport{Registrar: r}
+ chain := ds.GetChain("mychannel")
+ assert.Nil(t, chain)
+ assert.True(t, chain == nil)
+}