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

> robot_eye_grabber.cpp:196:21: warning: comparison of integers of different signs: 'int' and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]

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