return err instead of panic in Render

[Tevic]

This PR resolve issues like:
#2150

Change-Id: I3ce1afb327fea7a92a21e27649f7af87e286bf26

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[codecov]

Codecov Report

Merging #3039 (7fb2501) into master (580e7da) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 7fb2501 differs from pull request most recent head 4cfab1b. Consider uploading reports for the commit 4cfab1b to get more accurate results

@@            Coverage Diff             @@
##           master    #3039      +/-   ##
==========================================
- Coverage   98.60%   98.60%   -0.01%     
==========================================
  Files          41       41              
  Lines        3084     3082       -2     
==========================================
- Hits         3041     3039       -2     
  Misses         30       30              
  Partials       13       13              

Flag	Coverage Δ
go-1.13	∅ <ø> (∅)
go-1.14	∅ <ø> (∅)
go-1.15	∅ <ø> (∅)
go-1.16	98.60% <100.00%> (-0.01%)	⬇️
go-1.17	98.50% <100.00%> (-0.01%)	⬇️
macos-latest	98.60% <100.00%> (-0.01%)	⬇️
nomsgpack	98.58% <100.00%> (-0.01%)	⬇️
ubuntu-latest	98.60% <100.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
render/json.go	82.75% <100.00%> (-0.39%)	⬇️

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