check pc size

CMakeLists.txt.user

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE QtCreatorProject>
-<!-- Written by QtCreator 4.5.2, 2022-04-20T15:34:59. -->
+<!-- Written by QtCreator 4.5.2, 2022-07-04T13:50:33. -->
 <qtcreator>
  <data>
   <variable>EnvironmentId</variable>

apps/function/multi_traj_functions.cpp

@@ -323,11 +323,13 @@ vector<CloseTrajInfo> crossFilter(
 
             PointCloudExport periodCloud =
                     getCloudFromPeriod(pointClouds.at(oneRet.index), oneRet.periods.at(periodIndex));
+            if(periodCloud.size()){
                 pcl::io::savePCDFileBinary("/tmp/" + to_string(filteredTaskInfo[oneRet.index].meshId) +
                                            "_" + to_string(oneRet.periods.at(periodIndex).first) +
                                            ".pcd", periodCloud);
             }
         }
+    }
     return ret;
 }