"Undefined" as duplicate namespace `storage-ast-validator.js`

[ssolson]

Hey I have been running the sample-project and the hardhat-router continuously gives me the following error for multiple storage definitions

☠ Duplicate namespaces slot found!
  > undefined found in storage contracts OwnableStorage,ProxyStorage,GlobalStorage,InitializableStorage,SettingsStorage

I believe this is a bug.
A console log of the namespaces and duplicates found in storage-ast-validator.js are:

namespaces [
  { contractName: 'OwnableStorage', slot: undefined },
  { contractName: 'ProxyStorage', slot: undefined },
  { contractName: 'GlobalStorage', slot: undefined },
  { contractName: 'InitializableStorage', slot: undefined },
  { contractName: 'SettingsStorage', slot: undefined }
]
duplicates [
  {
    slot: undefined,
    contracts: [
      'OwnableStorage',
      'ProxyStorage',
      'GlobalStorage',
      'InitializableStorage',
      'SettingsStorage'
    ]
  }
]

As a hack for now I do not push the "undefined" slot to the errors starting at L36 of storage-ast-validator.js:

    if (duplicates) {
      const details = duplicates.map(
        (d) => `  > ${d.slot} found in storage contracts ${d.contracts}\n`
      );

      duplicates.map(
        (d) => {
          if (d.slot == undefined) 
            {console.log('Found undefined namespace')} 
          else {
            errors.push({
              msg: `Duplicate namespaces slot found!\n${details.join('')}`,
            });
          }
        }
      );

    }

Is the undefined namespace truly an issue?
Reproduction code ssolson/sample-project@8b4740d