[core] Fix default session

src/core/abc/manager.abc.ts

@@ -60,7 +60,7 @@ export abstract class SessionManager implements BeforeApplicationShutdown {
       const data: WAHAWebhook = {
         event: event,
         session: session.name,
-        metadata: session.sessionConfig.metadata,
+        metadata: session.sessionConfig?.metadata,
         me: me,
         payload: payload,
         engine: session.engine,

src/core/manager.core.ts

@@ -113,7 +113,7 @@ export class SessionManagerCore extends SessionManager {
   //
   async exists(name: string): Promise<boolean> {
     this.onlyDefault(name);
-    return !!this.session;
+    return this.session !== undefined;
   }
 
   isRunning(name: string): boolean {
@@ -246,7 +246,7 @@ export class SessionManagerCore extends SessionManager {
   getSession(name: string): WhatsappSession {
     this.onlyDefault(name);
     const session = this.session;
-    if (!session) {
+    if (session === undefined) {
       throw new NotFoundException(
         `We didn't find a session with name '${name}'. 
         Please start it first by using POST /sessions/${name}/start request`,

src/core/webhooks.core.ts

@@ -135,7 +135,7 @@ export class WebhookConductorCore implements WebhookConductor {
     const json: WAHAWebhook = {
       event: event,
       session: session.name,
-      metadata: session.sessionConfig.metadata,
+      metadata: session.sessionConfig?.metadata,
       me: me,
       payload: data,
       engine: session.engine,