bugfix: check 0 sized file

opencv-motion-detect/deployment/config_copy.json

+{
+   "data":{
+      "V2I0C7KC":{
+         "addr":"127.0.0.1",
+         "apiCloud":"http://127.0.0.1:8089",
+         "ipcs":[
+            {
+               "addr":"172.31.0.129",
+               "modules":{
+                  "evml":[
+                     {
+                        "area":200,
+                        "enabled":0,
+                        "iid":2,
+                        "post":30,
+                        "pre":3,
+                        "sn":"V2I0C7KC",
+                        "thresh":30,
+                        "entropy": 0.3,
+                        "type":"motion"
+                     }
+                  ],
+                  "evpuller":[
+                     {
+                        "addr":"127.0.0.1",
+                        "iid":1,
+                        "enabled": 1,
+                        "portPub":5556,
+                        "sn":"V2I0C7KC"
+                     }
+                  ],
+                  "evpusher":[
+                     {
+                        "enabled":1,
+                        "iid":1,
+                        "password":"",
+                        "sn":"V2I0C7KC",
+                        "token":"",
+                        "urlDest":"rtsp://40.73.41.176/V2I0C7KC",
+                        "user":""
+                     }
+                  ],
+                  "evslicer":[
+                     {
+                        "enabled":1,
+                        "iid":1,
+                        "path":"slices",
+                        "sn":"V2I0C7KC",
+                        "videoServerAddr": "http://40.73.41.176:10009/upload/evtvideos/"
+                     }
+                  ]
+               },
+               "password":"iLabService",
+               "port":554,
+               "proto":"rtsp",
+               "user":"admin",
+               "sn": "V2I0C7KC"
+            }
+         ],
+         "mqttCloud":"<cloud_addr>",
+         "portCloud":5556,
+         "portRouter":5550,
+         "proto":"zmq",
+         "sn":"V2I0C7KC"
+      }
+   },
+   "lastupdated":1567669674
+}
\ No newline at end of file