CopyBuffer: Skip Zero Elements

Avoid operating on invalid memory in `CopyBuffer` if the operation
is zero elements.

source/adios2/helper/adiosMemory.inl

@@ -147,7 +147,8 @@ void CopyToBuffer(std::vector<char> &buffer, size_t &position, const T *source,
                   const size_t elements) noexcept
 {
     const char *src = reinterpret_cast<const char *>(source);
-    std::copy(src, src + elements * sizeof(T), buffer.begin() + position);
+    if (elements > 0)
+        std::copy(src, src + elements * sizeof(T), buffer.begin() + position);
     position += elements * sizeof(T);
 }