chainntnfs: remove block info from conf detail copy

Noticed this while updating to latest master in another project:
If there are two notifications for the same output being registered and
the first one does _NOT_ request the block to be included, then the
second one also will not receive the block, even if it explicitly
requests it.
This is caused by the block being removed from the original confirmation
set instead of a copy (as it is done in NotifyHeight and
UpdateConfDetails).

chainntnfs/txnotifier.go

@@ -666,11 +666,15 @@ func (n *TxNotifier) RegisterConf(txid *chainhash.Hash, pkScript []byte,
 		// block along with the rest of the details. However not all
 		// clients want the block, so we make a copy here w/o the block
 		// if needed so we can give clients only what they ask for.
-		if !ntfn.includeBlock && confSet.details != nil {
-			confSet.details.Block = nil
+		confDetails := confSet.details
+		if !ntfn.includeBlock && confDetails != nil {
+			confDetailsCopy := *confDetails
+			confDetailsCopy.Block = nil
+
+			confDetails = &confDetailsCopy
 		}
 
-		err := n.dispatchConfDetails(ntfn, confSet.details)
+		err := n.dispatchConfDetails(ntfn, confDetails)
 		if err != nil {
 			return nil, err
 		}