Replace panic with nil return in newInjectedCompositeFieldsHandler

[m-Peter]

Description

There is no reason to panic when the location of a common.CompositeKindContract is not a common.AddressLocation. We can simply return nil, as we already do for stdlib.CryptoCheckerLocation.

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0639275) 79.23% compared to head (58bf115) 79.24%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2808   +/-   ##
=======================================
  Coverage   79.23%   79.24%           
=======================================
  Files         333      333           
  Lines       78753    78753           
=======================================
+ Hits        62401    62406    +5     
+ Misses      14042    14038    -4     
+ Partials     2310     2309    -1     

Flag	Coverage Δ
unittests	79.24% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
runtime/environment.go	92.62% <100.00%> (+0.31%)	⬆️

... and 1 file with indirect coverage changes

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[turbolent]

Thanks!