fix: LIME returns NaN weight if a feature contains a single value

[memoryz]

fix: LIME returns NaN weight if a feature contains a single value or when the sampler cannot obtain a different state for a feature due to data skew. It returns zero weights for all other features.

[memoryz]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

Merging #1117 (a96c0f7) into master (fe70f31) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1117      +/-   ##
==========================================
- Coverage   85.74%   85.72%   -0.03%     
==========================================
  Files         252      252              
  Lines       11605    11609       +4     
  Branches      599      605       +6     
==========================================
+ Hits         9951     9952       +1     
- Misses       1654     1657       +3     

Impacted Files	Coverage Δ
...icrosoft/ml/spark/explainers/LassoRegression.scala	96.96% <100.00%> (-3.04%)	⬇️
.../execution/streaming/continuous/HTTPSourceV2.scala	92.08% <0.00%> (-0.72%)	⬇️

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