Method nullCheck

www/js/_hyperscript.esm.js:2650–2654

(value, elt)

    return typeof ctor === "function" && value instanceof ctor;
  }
  nullCheck(value, elt) {
    if (value == null) {
      throw new Error("'" + elt.sourceFor() + "' is null");
    }
  }
  isEmpty(value) {
    return value == void 0 || value.length === 0;
  }