[bug]: lncli addinvoice --blind --amt 0 does not work

[ZZiigguurraatt]

Background

I'm getting the following error

$ lncli addinvoice --blind --amt 0
[lncli] rpc error: code = Unknown desc = could not build any blinded paths
$

$ lncli addinvoice --blind
[lncli] rpc error: code = Unknown desc = could not build any blinded paths
$

however, ,the following two cases work fine

lncli addinvoice --blind --amt 1

lncli addinvoice --blind --amt 2500000

This case also does not work

$ lncli addinvoice --blind --amt 2600000
[lncli] rpc error: code = Unknown desc = could not find any routes to self to use for blinded route construction
$

but that case, I kind of expect to fail on this node.

Your environment

$ lnd --version
lnd version 0.18.3-beta commit=v0.18.3-beta

Expected behaviour

Would expect an invoice with an invoice with no specified amount to be allowed with blinded paths. Not sure if this is a protocol limitation or LND limitation?

I realize that an invoice with an unspecified amount means any amount. I know LND can't assume anything can be routed through a blinded path it selects if it doesn't know how much is routed but it seems like in this case, LND should give a blinded path for the route with the most predicted capacity and if the payment fails, that is just the best it could do.