Added NPE checking on JobEngineClient response error handling

[Coduz]

This PR adds handling of possible NPE while checking content of the JobEngine web application response in case of error.

Related Issue
None

Description of the solution adopted
Added NPEs check and thrown proper exception

Screenshots
None

Any side note on the changes made
None

[codecov]

Codecov Report

Merging #3724 (e601aa6) into develop (f579ebb) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

❗ Current head e601aa6 differs from pull request most recent head 374d37b. Consider uploading reports for the commit 374d37b to get more accurate results

@@              Coverage Diff              @@
##             develop    #3724      +/-   ##
=============================================
- Coverage      55.38%   55.35%   -0.04%     
=============================================
  Files           1835     1835              
  Lines          34041    34045       +4     
  Branches        2717     2719       +2     
=============================================
- Hits           18855    18846       -9     
- Misses         14178    14193      +15     
+ Partials        1008     1006       -2     

Impacted Files	Coverage Δ
...apua/job/engine/client/JobEngineServiceClient.java	26.82% <0.00%> (-0.91%)	⬇️
...kapua/job/engine/client/JobStartOptionsClient.java	42.10% <0.00%> (-21.06%)	⬇️
...egistry/event/internal/DeviceEventServiceImpl.java	65.45% <0.00%> (-7.28%)	⬇️
...a/service/device/registry/internal/DeviceImpl.java	64.77% <0.00%> (-0.63%)	⬇️