Don't forward empty Span operations to backend

Author: franzpoeschel

include/openPMD/RecordComponent.tpp

@@ -366,6 +366,15 @@ RecordComponent::storeChunk(Offset o, Extent e, F &&createBuffer)
         dCreate.name = rc.m_name;
         IOHandler()->enqueue(IOTask(this, dCreate));
     }
+
+    if (size == 0)
+    {
+        // Don't forward this operation to the backend as it might create ugly
+        // zero-blocks in ADIOS2
+        setDirtyRecursive(true);
+        return DynamicMemoryView<T>();
+    }
+
     Parameter<Operation::GET_BUFFER_VIEW> getBufferView;
     getBufferView.offset = o;
     getBufferView.extent = e;

include/openPMD/Span.hpp

@@ -113,7 +113,10 @@ class DynamicMemoryView
     }
 
 public:
-    explicit DynamicMemoryView() = default;
+    explicit DynamicMemoryView()
+    {
+        m_param.out->backendManagedBuffer = false;
+    }
 
     /**
      * @brief Acquire the underlying buffer at its current position in memory.