BUG: Correctly identify comma seperated dtype strings

When parsing dtype strings, we should only consider them to
be comma seperated if there are commas not present in a
pair of square brackets.

Whilst we had a check for this already in the code there was
an off by 1 bug where we failed to consider the first character
of the string. This would lead to an infinite recursion when
trying to parse strings of the form `[i8,f8]`.

Fixes: #10440

0 files changed, 0 insertions, 0 deletions