ipn/ipnlocal: fix LocalBackend.WhoIs for self (#9472)

9538e9f970 broke LocalBackend.WhoIs
where you can no longer lookup yourself in WhoIs.
This occurs because the LocalBackend.peers map only contains peers.
If we fail to lookup a peer, double-check whether it is ourself.

Fixes #9470

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
Co-authored-by: Rhea Ghosh <rhea@tailscale.com>

ipn/ipnlocal/local.go

@@ -868,10 +868,17 @@ func (b *LocalBackend) WhoIs(ipp netip.AddrPort) (n tailcfg.NodeView, u tailcfg.
 			return zero, u, false
 		}
 	}
+	if b.netMap == nil {
+		return zero, u, false
+	}
 	n, ok = b.peers[nid]
 	if !ok {
+		// Check if this the self-node, which would not appear in peers.
+		if !b.netMap.SelfNode.Valid() || nid != b.netMap.SelfNode.ID() {
 			return zero, u, false
 		}
+		n = b.netMap.SelfNode
+	}
 	u, ok = b.netMap.UserProfiles[n.User()]
 	if !ok {
 		return zero, u, false