fix(buffer): fix Debug panic and fix formatting of overridden parts

[EdJoPaTo]

Fix panic in Debug for Buffer when width == 0.
Also corrects the output when symbols are overridden.

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Let's do some final testing for #1007… test runner aborts on panic in panic handler. Nice. 👻

[codecov]

Codecov Report

Attention: Patch coverage is 98.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 94.2%. Comparing base (699c2d7) to head (7bf8a63).

Files	Patch %	Lines
src/buffer/buffer.rs	98.0%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1098   +/-   ##
=====================================
  Coverage   94.2%   94.2%           
=====================================
  Files         61      61           
  Lines      14530   14538    +8     
=====================================
+ Hits       13693   13701    +8     
  Misses       837     837           

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[joshka]

Non blocking suggestions. Strong opinions weakly held here.

Can the commit message title be written in a more imperative form to describe the change in a way that makes more sense for the changelog? ("no" is ok here)