no-nil false positive

[graingert]

 switch (ham) {
    case "spam": return 3;
    case blockTypes.skew:
    default: return 4;
  }

should pass

same with:

if (foo) {
    return 3;
} else {
    return 4;
}

I've made a PR to fix eslint-plugin-better's explicit-return rule: idmitriev/eslint-plugin-better#3 using the consistent-return rule from eslint core