Fix NPE in GENERIC_VARIABLE_WRONG_DECLARATION

[kgevorkyan]

What's done:

• Fix bug - allow cases with wild card types
• Add tests

[codecov]

Codecov Report

Merging #1098 (83dc50c) into master (45f91c9) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #1098   +/-   ##
=========================================
  Coverage     83.40%   83.40%           
- Complexity     2453     2458    +5     
=========================================
  Files           102      102           
  Lines          6139     6141    +2     
  Branches       1839     1840    +1     
=========================================
+ Hits           5120     5122    +2     
  Misses          274      274           
  Partials        745      745           

Flag	Coverage Δ
unittests	83.40% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...les/chapter4/VariableGenericTypeDeclarationRule.kt	80.64% <100.00%> (+1.33%)	⬆️

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