Don't write chunks when there are no points.

Close #80

bu/CopcSupport.cpp

@@ -98,6 +98,13 @@ int CopcSupport::extraByteSize(const DimInfoList& dims) const
 /// \return  The offset of the chunk in the file.
 uint64_t CopcSupport::newChunk(const VoxelKey& key, int32_t size, int32_t count)
 {
+    // Chunks of size zero are a special case.
+    if (count == 0)
+    {
+        m_hierarchy[key] = { 0, 0, 0 };
+        return 0;
+    }
+
     uint64_t chunkStart = m_pointPos;
     m_pointPos += size;
     assert(count <= (std::numeric_limits<int32_t>::max)() && count >= 0);

bu/Processor.cpp

@@ -22,6 +22,7 @@
 
 #include <lazperf/lazperf.hpp>
 #include <lazperf/writers.hpp>
+#include <lazperf/readers.hpp>
 
 #include "Processor.hpp"
 #include "PyramidManager.hpp"
@@ -127,11 +128,6 @@ void Processor::sample(Index& accepted, Index& rejected)
 
 void Processor::write(Index& accepted, Index& rejected)
 {
-/**
-std::cerr << m_vi.key() << " Accepted/Rejected/num points = " <<
-    accepted.size() << "/" << rejected.size() << "/" << m_vi.numPoints() << "!\n";
-**/
-
     // If this is the final key, append any remaining file infos as accepted points and
     // write the accepted points as compressed.
     if (m_vi.key() == VoxelKey(0, 0, 0, 0))
@@ -469,6 +465,12 @@ void Processor::createChunk(const VoxelKey& key, pdal::PointViewPtr view)
 {
     using namespace pdal;
 
+    if (view->size() == 0)
+    {
+        m_manager.newChunk(key, 0, 0);
+        return;
+    }
+
     PointLayoutPtr layout = view->layout();
     int ebCount {0};
     for (DimType dim : m_extraDims)