Wrong output is returned, when keys use all bytes.

[wistoft]

Hej

I've found a case, where wrong output is returned.

const SharedMap = require("sharedmap");

const map = new SharedMap(4, 4, 4);

map.set("var0", "123");
map.set("var1", "123");

if ("123" !== map.get("var0")) {
  console.log("Got wrong output: " + map.get("var0"));
}

I've isolated the problem to missing space for zero bytes in keysData and valuesData.

And I've made PR for it