rpc: Require NodeStateStats object in getpeerinfo

There is no situation in which CNodeStateStats could be
missing for a legitimate reason - this can only happen if
there is a race condition between peer disconnection and
the getpeerinfo call, in which case the disconnected peer
doesn't need to be included in the response.

src/rpc/net.cpp

@@ -185,6 +185,14 @@ static RPCHelpMan getpeerinfo()
         UniValue obj(UniValue::VOBJ);
         CNodeStateStats statestats;
         bool fStateStats = peerman.GetNodeStateStats(stats.nodeid, statestats);
+        // GetNodeStateStats() requires the existence of a CNodeState and a Peer object
+        // to succeed for this peer. These are created at connection initialisation and
+        // exist for the duration of the connection - except if there is a race where the
+        // peer got disconnected in between the GetNodeStats() and the GetNodeStateStats()
+        // calls. In this case, the peer doesn't need to be reported here.
+        if (!fStateStats) {
+            continue;
+        }
         obj.pushKV("id", stats.nodeid);
         obj.pushKV("addr", stats.m_addr_name);
         if (stats.addrBind.IsValid()) {