storeChunk with zero extent

[ax3l]

Describe the bug When calling storeChunk with a zero extent, bad things happen.

Have to check again, but either some backends crashed, hung or were made empty().

To Reproduce Re: https://github.com/ECP-WarpX/WarpX/pull/1898#discussion_r745008290

Python:

import openpmd_api

# ...

or C++

#include <openPMD/openPMD.hpp>

// ...

or command line script, example:

# in directory $HOME/src/openPMD-api
mkdir build && cd build

cmake ..
# fails with:
#   bash: cmake: command not found

Expected behavior A clear and concise description of what you expected to happen.

Software Environment

• version of openPMD-api: 0.14.3
• installed openPMD-api via: any
• operating system: Linux
• machine: Ubuntu
• name and version of Python implementation: N/A
• version of HDF5: [e.g. 1.12.0]
• version of ADIOS1: [e.g. 1.13.1]
• version of ADIOS2: [e.g. 2.7.1]
• name and version of MPI: [e.g. OpenMPI 4.1.1]

Additional context Re: https://github.com/ECP-WarpX/WarpX/pull/1898#discussion_r745008290

[ax3l]

I cannot reproduce which test case and openPMD backend (HDF5 or ADIOS2) @RevathiJambunathan used in the linked issue, since we forgot to document it: https://github.com/ECP-WarpX/WarpX/pull/1898#discussion_r745008290