getMany with an empty array as keys crashes the whole process

[oldrich-svec]

In the following many variable should contain an empty array but instead the whole process crashes.

const lmdb = require('lmdb')

const db = lmdb.open('test')

async function main() {
    const many = await db.getMany([])
    console.log(many)
    console.log('end')
}

main()

[kriszyp]

Fix published in v2.2.6