Bug report

Describe the bug
Writing out a cmesh/forest with an empty process results in the assertion

[libsc 0] Abort: Assertion 'num_local_trees > 0'
[libsc 0] Abort: /localdata1/holk_jo/coding/source/t8code/feature-extend_lfn_to_ghosts/src/t8_cmesh/t8_cmesh.cxx:2389

caused by the t8_cmesh_get_local_bounding_box

To Reproduce
Take a forest with N elements on P>N processes and write out a vtk file.

Expected behavior
No assertions should be caused. Empty partitioned should be able to write out.

Log files
N/A

Environment (please complete the following information):

• OS: Ubuntu 22.04,

Estimated priority
Which of these is most applicable (remove the others):

"Priority: high" Should be solved as soon as possible

"Priority: medium" Should be solved within half a year

"Priority: low" Should be solved eventually

Additional context