Closing ledger multiple times results in panic

An initial fix to avoid the panic. See JIRA for further
details regarding why the ledger is being closed more than
once. I'm not familiar enough with gossip at the moment to
determine the proper plan of action for the code that's causing
this.

FAB-15915

Change-Id: I79a0009b7fec401b0351d96ee7f1a495ccf05c98
Signed-off-by: Will Lahti <wtlahti@us.ibm.com>

Author: wlahti

core/ledger/ledgermgmt/ledger_mgmt.go

@@ -164,9 +164,11 @@ func (m *LedgerMgr) getOpenedLedger(ledgerID string) (ledger.PeerLedger, error)
 func (m *LedgerMgr) closeLedger(ledgerID string) {
 	m.lock.Lock()
 	defer m.lock.Unlock()
-	l := m.openedLedgers[ledgerID]
-	l.Close()
-	delete(m.openedLedgers, ledgerID)
+	l, ok := m.openedLedgers[ledgerID]
+	if ok {
+		l.Close()
+		delete(m.openedLedgers, ledgerID)
+	}
 }
 
 // closableLedger extends from actual validated ledger and overwrites the Close method

core/ledger/ledgermgmt/ledger_mgmt_test.go

@@ -54,6 +54,9 @@ func TestLedgerMgmt(t *testing.T) {
 
 	l := ledgers[2]
 	l.Close()
+	// attempt to close the same ledger twice and ensure it doesn't panic
+	assert.NotPanics(t, l.Close)
+
 	l, err = ledgerMgr.OpenLedger(ledgerID)
 	assert.NoError(t, err)