test: check inspect array with empty string key

test: check inspect array with empty string key · nodejs/node@9cebe82

Original file line number	Diff line number	Diff line change
`@@ -831,6 +831,12 @@ checkAlignment(new Map(big_array.map(function(y) { return [y, null]; })));`
`831`	`831`	`assert.strictEqual(util.inspect(x), '{}');`
`832`	`832`	`}`
`833`	`833`
	`834`	`+{`
	`835`	`+const x = [];`
	`836`	`+x[''] = 1;`
	`837`	`+assert.strictEqual(util.inspect(x), '[ \'\': 1 ]');`
	`838`	`+}`
	`839`	`+`
`834`	`840`	`// The following maxArrayLength tests were introduced after v6.0.0 was released.`
`835`	`841`	`// Do not backport to v5/v4 unless all of`
`836`	`842`	`// https://github.com/nodejs/node/pull/6334 is backported.`