Improve error message

src/custom-functions/v3/bcode.ts

@@ -29,8 +29,12 @@ export function bcode(
   }
 
   const setting = Setting.load()
-  if (!setting.token) {
-    throw new Error('<<APIキーが有効ではありません>>')
+  if (setting.token === null) {
+    throw new Error('<<APIキーの読み取りに失敗しました>>')
+  }
+
+  if (setting.token === '') {
+    throw new Error('<<APIキーが設定されていません>>')
   }
 
   if (typeof intent === 'string' && intent.toUpperCase() === Setting.companyIntent) {

src/setting.ts

@@ -15,12 +15,12 @@ export class Setting {
   static readonly companyIntent = 'COMPANY'
 
   private constructor(
-    private _token: string,
+    private _token: string | null,
     private _ondemandApiEnabled: boolean,
     private _ondemandApiCallMode: 'default' | 'force'
   ) {}
 
-  public get token(): string {
+  public get token(): string | null {
     return this._token
   }