fix: Prevent ClassCastException in ErrorUtils

[ShridharGoel]

Fixes #1589

Checklist:

• I have checked for PMD and check-style issues
• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream development branch.

Changes:

Added condition if (throwable instanceof HttpException)

[codecov]

Codecov Report

Merging #1590 into development will decrease coverage by <.01%.
The diff coverage is 76.92%.

@@                Coverage Diff                @@
##             development    #1590      +/-   ##
=================================================
- Coverage          24.78%   24.77%   -0.01%     
  Complexity           800      800              
=================================================
  Files                238      238              
  Lines               8970     8972       +2     
  Branches             374      376       +2     
=================================================
  Hits                2223     2223              
  Misses              6663     6663              
- Partials              84       86       +2

Impacted Files	Coverage Δ	Complexity Δ
.../java/com/eventyay/organizer/utils/ErrorUtils.java	78.57% <76.92%> (-2.92%)	11 <0> (ø)

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