fix/qr code no usable

[Fernando-hub527]

Description
fix bug in matrix code and qr-code generation

Related Issue
#476

Checklist

check with "x", ONLY IF APPLIED to your change

• All methods associated with structs has func (<first letter of struct> *struct) method() {} name style.
• Wrote unit tests for new/changed features.
• Followed the unit test when,should naming pattern.
• All mocks created with m := mocks.NewConstructor(t).
• All mocks using m.EXPECT().MethodName() method to mock methods.
• Updated docs/doc.go and docs/*
• Updated example_test.go.
• Updated README.md
• New public methods/structs/interfaces has comments upside them explaining they responsibilities
• Executed make dod with none issues pointed out by golangci-lint

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (master@b7ed197). Learn more about missing BASE report.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #477   +/-   ##
=========================================
  Coverage          ?   87.18%           
=========================================
  Files             ?       61           
  Lines             ?     2315           
  Branches          ?        0           
=========================================
  Hits              ?     2018           
  Misses            ?      265           
  Partials          ?       32           

Flag	Coverage Δ
unittests	87.18% <100.00%> (?)

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