Handle JSONDecodeError in OAuth error handler

[philippjfr]

No description provided.

[codecov]

Codecov Report

Merging #1508 into master will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1508      +/-   ##
==========================================
- Coverage   86.27%   86.26%   -0.02%     
==========================================
  Files         143      143              
  Lines       15786    15789       +3     
==========================================
  Hits        13620    13620              
- Misses       2166     2169       +3     

Impacted Files	Coverage Δ
panel/auth.py	34.24% <0.00%> (-0.41%)	⬇️

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