### What does this PR do?
Closes#25505. This adjusts the byte length check in `DataCell:
fromBytes` to 12 bytes instead of 16, as zero-dimensional arrays will
have a shorter preamble.
### How did you verify your code works?
Test suite passes, and I've added a new test that fails in the main
branch but passes with this change. The issue only seems to crop up when
a connection is _reused_, which is curious.