[DiagnosticLogs] When the size of the TransferFileDesignator is 0, th…

…e server should returns CONSTRAINT_ERROR (project-chip#32207)

src/app/clusters/diagnostic-logs-server/diagnostic-logs-server.cpp

@@ -132,6 +132,8 @@ void DiagnosticLogsServer::HandleLogRequestForBdx(CommandHandler * commandObj, c
     // INVALID_COMMAND.
     VerifyOrReturn(transferFileDesignator.HasValue(), commandObj->AddStatus(path, Status::InvalidCommand));
 
+    VerifyOrReturn(transferFileDesignator.Value().size() > 0, commandObj->AddStatus(path, Status::ConstraintError));
+
     VerifyOrReturn(transferFileDesignator.Value().size() <= kMaxFileDesignatorLen,
                    commandObj->AddStatus(path, Status::ConstraintError));