fix: do not panic on nil object

[SVilgelm]

fix #20 for the panic on json.Marshal(nil) code

[codecov-commenter]

Codecov Report

Merging #21 (76108a1) into main (27a84af) will increase coverage by 0.11%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main      #21      +/-   ##
==========================================
+ Coverage   95.23%   95.34%   +0.11%     
==========================================
  Files           1        1              
  Lines         126      129       +3     
==========================================
+ Hits          120      123       +3     
  Misses          4        4              
  Partials        2        2              

Impacted Files	Coverage Δ
musttag.go	95.34% <100.00%> (+0.11%)	⬆️

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[tmzane]

I've also found out that arg.Obj may be nil if the argument is a global variable defined in a separate file 🤔. I'll fix that in a separate PR.

[SVilgelm]

I've also found out that arg.Obj may be nil if the argument is a global variable defined in a separate file 🤔. I'll fix that in a separate PR.

Oh, cool that you found it. I will test the linter on our code. Thank you for your work