bugfix: fix map decode

[tonybase]

fix #2468

[codecov-commenter]

Codecov Report

Merging #2979 (6135a19) into main (a09f4d8) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 6135a19 differs from pull request most recent head ab6ea11. Consider uploading reports for the commit ab6ea11 to get more accurate results

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@@            Coverage Diff             @@
##             main    #2979      +/-   ##
==========================================
+ Coverage   84.32%   84.34%   +0.01%     
==========================================
  Files          88       88              
  Lines        3981     3986       +5     
==========================================
+ Hits         3357     3362       +5     
  Misses        448      448              
  Partials      176      176              

Files Changed	Coverage Δ
encoding/form/proto_decode.go	64.28% <100.00%> (+0.72%)	⬆️