bsddialog(1): Improve --hline (help subtitle)

[asiciliano]

Summary

Improvement for bsdconfig(8): avoid to draw delimiters (or spaces) on the bottom line if --hline is an empty string.

Test Plan

Before:

% bsddialog --hline "" --yesno test 0 0

┌───────────────────┐
│ test              │  
├───────────────────┤  
│[ Yes  ]   [  No  ]│  
└────────  ─────────┘

The problem is on the bottom line.

After the review
% bsddialog --hline "" --yesno test 0 0

┌───────────────────┐
│ test              │  
├───────────────────┤  
│[ Yes  ]   [  No  ]│  
└───────────────────┘

All right.

[asiciliano]

Closed by commit https://cgit.freebsd.org/src/commit/?id=9225c909fbc1478a1803e647d89f2e63cbac98f2 bsddialog(1): Improve --hline (help subtitle)