Fix warnings in io/robot_eye_grabber.cpp
Fix warnings in io/robot_eye_grabber.cpp

> robot_eye_grabber.cpp:169:21: warning: comparison of integers of different signs: 'int' and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]

KevenRing/pcl,shyamalschandra/pcl,shivmalhotra/pcl,pkuhto/pcl,starius/pcl,shangwuhencc/pcl,shivmalhotra/pcl,LZRS/pcl,jakobwilm/pcl,KevenRing/vlp,fanxiaochen/mypcltest,lebronzhang/pcl,kanster/pcl,chatchavan/pcl,stefanbuettner/pcl,shyamalschandra/pcl,stfuchs/pcl,zavataafnan/pcl-truck,DaikiMaekawa/pcl,closerbibi/pcl,chatchavan/pcl,raydtang/pcl,damienjadeduff/pcl,ResByte/pcl,fanxiaochen/mypcltest,msalvato/pcl_kinfu_highres,sbec/pcl,chenxingzhe/pcl,zhangxaochen/pcl,MMiknis/pcl,mikhail-matrosov/pcl,ResByte/pcl,3dtof/pcl,shyamalschandra/pcl,jakobwilm/pcl,fanxiaochen/mypcltest,chenxingzhe/pcl,DaikiMaekawa/pcl,RufaelDev/pcc-mp3dg,starius/pcl,stfuchs/pcl,chenxingzhe/pcl,mschoeler/pcl,nh2/pcl,Tabjones/pcl,drmateo/pcl,jeppewalther/kinfu_segmentation,soulsheng/pcl,KevenRing/pcl,locnx1984/pcl,LZRS/pcl,ResByte/pcl,locnx1984/pcl,sbec/pcl,lydhr/pcl,pkuhto/pcl,damienjadeduff/pcl,nh2/pcl,shivmalhotra/pcl,cascheberg/pcl,fskuka/pcl,nikste/pcl,drmateo/pcl,cascheberg/pcl,v4hn/pcl,soulsheng/pcl,lebronzhang/pcl,ipa-rmb/pcl,ipa-rmb/pcl,krips89/pcl_newfeatures,MMiknis/pcl,wgapl/pcl,3dtof/pcl,lydhr/pcl,simonleonard/pcl,stfuchs/pcl,mschoeler/pcl,stefanbuettner/pcl,ResByte/pcl,kanster/pcl,pkuhto/pcl,krips89/pcl_newfeatures,LZRS/pcl,nh2/pcl,chenxingzhe/pcl,stefanbuettner/pcl,soulsheng/pcl,locnx1984/pcl,srbhprajapati/pcl,stfuchs/pcl,damienjadeduff/pcl,starius/pcl,KevenRing/vlp,damienjadeduff/pcl,the-glu/pcl,MMiknis/pcl,zavataafnan/pcl-truck,jakobwilm/pcl,jeppewalther/kinfu_segmentation,closerbibi/pcl,v4hn/pcl,shyamalschandra/pcl,MMiknis/pcl,fskuka/pcl,the-glu/pcl,v4hn/pcl,damienjadeduff/pcl,jeppewalther/kinfu_segmentation,the-glu/pcl,nh2/pcl,closerbibi/pcl,mschoeler/pcl,mikhail-matrosov/pcl,chenxingzhe/pcl,simonleonard/pcl,krips89/pcl_newfeatures,shangwuhencc/pcl,pkuhto/pcl,3dtof/pcl,Tabjones/pcl,chatchavan/pcl,lydhr/pcl,jeppewalther/kinfu_segmentation,ipa-rmb/pcl,lydhr/pcl,wgapl/pcl,stefanbuettner/pcl,simonleonard/pcl,nikste/pcl,msalvato/pcl_kinfu_highres,KevenRing/pcl,chatchavan/pcl,drmateo/pcl,zhangxaochen/pcl,zavataafnan/pcl-truck,sbec/pcl,lydhr/pcl,srbhprajapati/pcl,stfuchs/pcl,fanxiaochen/mypcltest,RufaelDev/pcc-mp3dg,krips89/pcl_newfeatures,Tabjones/pcl,sbec/pcl,simonleonard/pcl,mschoeler/pcl,raydtang/pcl,pkuhto/pcl,drmateo/pcl,wgapl/pcl,DaikiMaekawa/pcl,srbhprajapati/pcl,KevenRing/vlp,kanster/pcl,the-glu/pcl,lebronzhang/pcl,ipa-rmb/pcl,srbhprajapati/pcl,fskuka/pcl,zhangxaochen/pcl,3dtof/pcl,LZRS/pcl,stefanbuettner/pcl,cascheberg/pcl,mschoeler/pcl,nikste/pcl,soulsheng/pcl,KevenRing/vlp,DaikiMaekawa/pcl,lebronzhang/pcl,shangwuhencc/pcl,KevenRing/pcl,v4hn/pcl,shyamalschandra/pcl,mikhail-matrosov/pcl,shivmalhotra/pcl,msalvato/pcl_kinfu_highres,srbhprajapati/pcl,Tabjones/pcl,jeppewalther/kinfu_segmentation,fskuka/pcl,jakobwilm/pcl,cascheberg/pcl,nikste/pcl,locnx1984/pcl,jakobwilm/pcl,ResByte/pcl,LZRS/pcl,krips89/pcl_newfeatures,kanster/pcl,mikhail-matrosov/pcl,msalvato/pcl_kinfu_highres,locnx1984/pcl,msalvato/pcl_kinfu_highres,closerbibi/pcl,KevenRing/pcl,Tabjones/pcl,raydtang/pcl,nikste/pcl,drmateo/pcl,zavataafnan/pcl-truck,cascheberg/pcl,closerbibi/pcl,RufaelDev/pcc-mp3dg,RufaelDev/pcc-mp3dg,zhangxaochen/pcl,v4hn/pcl,zhangxaochen/pcl,soulsheng/pcl,the-glu/pcl,shangwuhencc/pcl,wgapl/pcl,DaikiMaekawa/pcl,wgapl/pcl,lebronzhang/pcl,MMiknis/pcl,raydtang/pcl,3dtof/pcl,KevenRing/vlp,RufaelDev/pcc-mp3dg,sbec/pcl,starius/pcl,shangwuhencc/pcl,fskuka/pcl,ipa-rmb/pcl,mikhail-matrosov/pcl,zavataafnan/pcl-truck,simonleonard/pcl,shivmalhotra/pcl,fanxiaochen/mypcltest,kanster/pcl,raydtang/pcl,starius/pcl