析构时，deleteCamera增加handle置位的操作，防止重复关闭报错

chenshijun

2019-07-29 69895028b74737228e76005f88b9aaf95136ec96

 csrc/ffmpeg/property/VideoProp.cpp

@@ -17,6 +17,7 @@
   ,udp_port_x_(5000)
   ,udp_port_y_(65000)
    ,gpu_acc_(true)
   ,gpu_index_(-1)
    ,sample_aspect_ratio_(AVRational{0,1})
   {}