fix: Set cc, bcc default to empty string if unavailable (#3387)

app/javascript/dashboard/api/specs/inbox/message.spec.js

@@ -35,12 +35,14 @@ describe('#ConversationAPI', () => {
         message: 'test content',
         echoId: 12,
         isPrivate: true,
+
         file: new Blob(['test-content'], { type: 'application/pdf' }),
       });
       expect(formPayload).toBeInstanceOf(FormData);
       expect(formPayload.get('content')).toEqual('test content');
       expect(formPayload.get('echo_id')).toEqual('12');
       expect(formPayload.get('private')).toEqual('true');
+      expect(formPayload.get('cc_emails')).toEqual('');
     });
 
     it('builds object payload if file is not available', () => {
@@ -56,6 +58,8 @@ describe('#ConversationAPI', () => {
         private: false,
         echo_id: 12,
         content_attributes: { in_reply_to: 12 },
+        bcc_emails: '',
+        cc_emails: '',
       });
     });
   });