Fix radio button with zero value

[MrCrayon]

Removed some insanity and simplified with new null coalescing operator.

$selected_value should be in priority order:
value sent
value saved in db
default set in BREAD settings
NULL

Fixes #5221

[codecov]

Codecov Report

Merging #5223 (35a0840) into 1.4 (3c2d314) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                1.4    #5223   +/-   ##
=========================================
  Coverage     63.37%   63.37%           
  Complexity     1394     1394           
=========================================
  Files           195      195           
  Lines          4120     4120           
=========================================
  Hits           2611     2611           
  Misses         1509     1509           

---

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[codecov-commenter]

Codecov Report

Merging #5223 (1b71233) into 1.4 (5e05e4a) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                1.4    #5223   +/-   ##
=========================================
  Coverage     63.45%   63.45%           
  Complexity     1393     1393           
=========================================
  Files           195      195           
  Lines          4116     4116           
=========================================
  Hits           2612     2612           
  Misses         1504     1504           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5e05e4a...1b71233. Read the comment docs.