fix: handle pnpm empty lockfiles

[gemaxim]

Handle no dependencies projects for pnpm:

• pnpm@7 does not create a lockfile
• pnpm@8 and pnpm@9 creates a lockfile without packages/snapshots fields

It should return a dep graph with only the root package.

[snyksec]

:tada: This PR is included in version 1.58.12 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: