Fix a format-truncation compiler warning.

[nksauter]

gcc compiler produces a warning: 'snprintf' output truncated before the last format character,
and a note: 'snprintf' output 16 bytes into a destination of size 15.
The fix is to adjust the format string to 14 whitespaces, allowing the
15th position to be used for null-termination.

[codecov]

Codecov Report

Merging #1836 (a6c53b2) into main (fa58b57) will not change coverage.
The diff coverage is n/a.

❗ Current head a6c53b2 differs from pull request most recent head 849a5dc. Consider uploading reports for the commit 849a5dc to get more accurate results

@@           Coverage Diff           @@
##             main    #1836   +/-   ##
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  Coverage   67.15%   67.15%           
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  Files         617      617           
  Lines       69427    69427           
  Branches     9656     9656           
=======================================
  Hits        46621    46621           
  Misses      20867    20867           
  Partials     1939     1939           

[ndevenish]

It looks like this line possibly isn't necessary at all. Or at least ostringstream would be cleaner and less confusing.

However, I'm pretty sure this is the reflection viewer and basically disused, so not really worth understanding what the routine is trying to do in the first place.