improve database detect

package.json

 {
   "name": "koishi-plugin-thesaurus",
-  "version": "1.0.3",
+  "version": "1.0.4",
   "description": "Koishi.js chat plugin for https://github.com/Kyomotoi/AnimeThesaurus",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/plugin.ts

@@ -147,8 +147,8 @@ export class MyPlugin {
   async apply(ctx: Context, config: MyPluginConfigLike) {
     this.ctx = ctx;
     this.config = schemaTransform(MyPluginConfig, config);
-    ctx.on('connect', () => {
-      if (ctx.database && this.config.useDatabase) this.useDatabase = true;
+    ctx.on('service/database', () => {
+      if (this.config.useDatabase) this.useDatabase = !!ctx.database;
     });
     ctx.cache.table('thesaurusChatSession', {
       maxAge: this.config.chatTimeout,