Fix for issue 181

[bsterzinger]

Webpack build in Angular with namedChunks set to false emits the zeroth script with an id of 0. This means its integrity hash is not added to sriHashes as depChunks.id evaluates as falsy. This means the zeroth script generated by webpack has its integrity property set to undefined triggering the following error:

Error parsing 'integrity' attribute ('undefined'). The hash algorithm must be one of 'sha256', 'sha384', or 'sha512', followed by a '-' character.

By explicitly accepting 0 as an id, this non-breaking error will be avoided.