Audiomixerboard: Fix extra blank line when musician name length % iBreakPos == 0

[dtinth]

Short description of changes
Fix a bug where a blank line is shown after some client’s name in the mixer board when their name’s length is divisible by iBreakPos (which is 8 or 4).

CHANGELOG: Client: Fix a bug where a blank line is shown after some client’s name in the mixer board in some conditions.

Context: Fixes an issue?
There is a regression introduced in Jamulus 3.8.2 by #1994 / #1993 (which fixes #1451) causing some musician’s name to have an extra blank line at the end.

Does this change need documentation? What needs to be documented and how?
No

Status of this Pull Request
Working fix

What is missing until this pull request can be merged?
N/A

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above

[pljones]

Might be complicated but it makes sense.

[hoffie]

Thanks! Looks good and works as expected.
(I've slightly edited the commit description and therefore force-pushed. Merging now despite not all checks having finished again, but the commit content is unchanged)