minor optimization

7 jobs for selection_pointcloud in 66 minutes and 42 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #26595
Apple
Mac-Cpp11

00:38:26

passed #26594
Qt551 VS2013
VS2013-Qt-5.5.1-x64

00:25:22

passed #26593
Qt56 VS2015
VS2015-Qt-5.6.0-x32

00:22:11

passed #26592
Qt56 VS2015
VS2015-Qt-5.6.0-x64

00:26:46

passed #26590
MultiThreads Linux
clang-c++11-Qt5

00:10:53

passed #26591
MultiThreads Linux
cppcheck

00:03:06

passed #26589
Linux
gcc-c++11-Qt5

00:03:40