Using an equal sign with short/alias options and an empty string

[ehmicky]

Short options do not seem to work when using an equal sign and an empty string.

Example:

// yargs.js
const yargs = require('yargs')
console.log(yargs.option('opt', { alias: 'o' }).parse())

$ node yargs.js -o ""
{ _: [], o: '', opt: '', '$0': 'yargs.js' }
$ node yargs.js -o=""
{ _: [], o: true, opt: true, '=': true, '$0': 'yargs.js' }

Note that this works correctly when not using an empty string:

$ node yargs.js -o "value"
{ _: [], o: 'value', opt: 'value', '$0': 'yargs.js' }
$ node yargs.js -o="value"
{ _: [], o: 'value', opt: 'value', '$0': 'yargs.js' }

Using yargs 16.2.0 on Node 15.6.0.