wallet: minor style fixes, and remove null JSON fields.

Our policy is generally to omit fields which aren't sensible.
Also, @niftynei points out the spacing in for loops.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_wallet.py

@@ -472,8 +472,16 @@ def test_transaction_annotations(node_factory, bitcoind):
     assert(output['type'] == 'deposit' and output['satoshis'] == '1000000000msat')
 
     # ... and all other output should be change, and have no annotations
-    types = set([o['type'] for i, o in enumerate(tx['outputs']) if i != idx])
+    types = []
-    assert(set([None]) == types)
+    for i, o in enumerate(tx['outputs']):
+        if i == idx:
+            continue
+        if 'type' in o:
+            types.append(o['type'])
+        else:
+            types.append(None)
+
+    assert(set([None]) == set(types))
 
     ##########################################################################
     # Let's now open a channel. The opener should get the funding transaction

wallet/walletrpc.c

@@ -936,13 +936,9 @@ static void json_transaction_details(struct json_stream *response,
 #if EXPERIMENTAL_FEATURES
 		if (tx->annotation.type != 0)
 			json_add_txtypes(response, "type", tx->annotation.type);
-		else
-			json_add_null(response, "type");
 
 		if (tx->annotation.channel.u64 != 0)
 			json_add_short_channel_id(response, "channel", &tx->annotation.channel);
-		else
-			json_add_null(response, "channel");
 #endif
 		json_add_u32(response, "locktime", wtx->locktime);
 		json_add_u32(response, "version", wtx->version);
@@ -959,12 +955,8 @@ static void json_transaction_details(struct json_stream *response,
 			const char *txtype = txtype_to_string(ann->type);
 			if (txtype != NULL)
 				json_add_string(response, "type", txtype);
-			else
-				json_add_null(response, "type");
 			if (ann->channel.u64 != 0)
 				json_add_short_channel_id(response, "channel", &ann->channel);
-			else
-				json_add_null(response, "channel");
 #endif
 
 			json_object_end(response);
@@ -993,13 +985,9 @@ static void json_transaction_details(struct json_stream *response,
 			const char *txtype = txtype_to_string(ann->type);
 			if (txtype != NULL)
 				json_add_string(response, "type", txtype);
-			else
-				json_add_null(response, "type");
 
 			if (ann->channel.u64 != 0)
 				json_add_short_channel_id(response, "channel", &ann->channel);
-			else
-				json_add_null(response, "channel");
 #endif
 			json_add_hex(response, "scriptPubKey", out->script, out->script_len);