Bug in pointcloudmapping.cc PointCloudMapping::viewer()

[MelancholyMethane]

A lock should be added when calling generatePointCloud, or the addresses of the vectors may shift when other threads execute the push_back operation.
This is especially likely to happen in a device where the memory is limited and the memory block allocated initially is not large enough. If it happens, a segmentation fault will result.
Wrong:

        for ( size_t i=lastKeyframeSize; i<N ; i++ )
        {
            PointCloud::Ptr p = generatePointCloud( keyframes[i],semanticImgs_color[i], semanticImgs[i],colorImgs[i], depthImgs[i] );
	        *KfMap += *p;
	        *globalMap += *p;	    
        }

A possible correction:

        for ( size_t i=lastKeyframeSize; i<N ; i++ )
        {
            unique_lock<mutex> lck(keyframeMutex);
            PointCloud::Ptr p = generatePointCloud( keyframes[i],semanticImgs_color[i], semanticImgs[i],colorImgs[i], depthImgs[i] );
	        *KfMap += *p;
	        *globalMap += *p;	    
        }