Template with no inputs looses outputs

[3sGgpQ8H]

I have the following circuit:

template Foo () {
//  signal input y;
  signal output x;
  x <== 13;
}
template Bar () {
  component foo = Foo ();
//  foo.y <== 12;
  foo.x === 13;
}
component main = Bar ();

It compiles successfully, but what I run snarkjs calculatewitness it reports the following error:

Error: Signal not initialized: main.foo.x
    at RTCtx.getSignalFullName (/usr/local/lib/node_modules/snarkjs/src/calculateWitness.js:220:19)
    at RTCtx.getPin (/usr/local/lib/node_modules/snarkjs/src/calculateWitness.js:214:21)
    at Object.__f [as Bar] (eval at Circuit (/usr/local/lib/node_modules/snarkjs/src/circuit.js:46:33), <anonymous>:2:20)
    at RTCtx.triggerComponent (/usr/local/lib/node_modules/snarkjs/src/calculateWitness.js:126:41)
    at calculateWitness (/usr/local/lib/node_modules/snarkjs/src/calculateWitness.js:43:45)
    at Circuit.calculateWitness (/usr/local/lib/node_modules/snarkjs/src/circuit.js:59:16)
    at Object.<anonymous> (/usr/local/lib/node_modules/snarkjs/cli.js:308:29)
    at Module._compile (internal/modules/cjs/loader.js:701:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
    at Module.load (internal/modules/cjs/loader.js:600:32)
ERROR: Error: Signal not initialized: main.foo.x

I played with this code a bit and it seems that in case template has no inputs, something bad happens with its outputs. Uncommenting commented lines makes it work.

> circom --version
0.0.31
> snarkjs --version
0.1.18
> uname -a
Darwin MacBookPro 19.0.0 Darwin Kernel Version 19.0.0: Wed Sep 25 20:18:50 PDT 2019; root:xnu-6153.11.26~2/RELEASE_X86_64 x86_64

[adamalexandru4]

I also have the same type of error. Any solution?