assertion failure in H5D__mpio_collective_filtered_vec_io

[qkoziol]

Describe the bug
Crash in t_pmulti_dset test:

Configuration:
Layout: Chunked
Shape same: No
I/O type: Single
MPI I/O type: Collective
Low level MPI I/O:Collective
Type conversion: No
Data filter: Yes
Testing random I/O Assertion failed: (vec_idx < iovec_count), function H5D__mpio_collective_filtered_vec_io, file H5Dmpio.c, line 5498.

===================================================================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= PID 91513 RUNNING AT Nile.local
= EXIT CODE: 6
= CLEANING UP REMAINING PROCESSES
= YOU CAN IGNORE THE BELOW CLEANUP MESSAGES

YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Terminated: 15 (signal 15)
This typically refers to a problem with your application.
Please see the FAQ page for debugging suggestions
7.23 real 33.77 user 8.05 sys
make[3]: *** [t_pmulti_dset.chkexe_] Error 1
make[2]: *** [build-check-p] Error 1
make[1]: *** [test] Error 2
make: *** [check-am] Error 2

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

Platform (please complete the following information)
Current version of the develop branch, on my Mac, with this configuration:

env CC=mpicc CXX=mpic++ FC=mpif90 ../hdf5/configure --enable-build-mode=debug --enable-maintainer-mode --enable-developer-warnings --enable-diags --disable-shared --enable-parallel --enable-cxx --enable-fortran --enable-map-api --enable-threadsafe --enable-build-all --enable-mirror-vfd --enable-subfiling-vfd --enable-unsupported

Additional context
Add any other context about the problem here.

[qkoziol]

@jhendersonHDF - related to your recent PR?

[jhendersonHDF]

Hmm yes, though I don't know why I didn't see this.