Fix Hanging the Service when Returning Array

[DimuthuMadushan]

Purpose

Fixes: #1250

Examples

N/A

Checklist

• Linked to an issue
• Updated the changelog
• Added tests

[codecov]

Codecov Report

Merging #178 (fc6f32c) into master (d160352) will increase coverage by 0.01%.
The diff coverage is 95.00%.

@@             Coverage Diff              @@
##             master     #178      +/-   ##
============================================
+ Coverage     89.73%   89.74%   +0.01%     
- Complexity      232      233       +1     
============================================
  Files            42       42              
  Lines          1821     1823       +2     
  Branches        699      700       +1     
============================================
+ Hits           1634     1636       +2     
  Misses          162      162              
  Partials         25       25              

Impacted Files	Coverage Δ	Complexity Δ
...b/graphql/runtime/engine/CallableUnitCallback.java	95.19% <92.85%> (+0.09%)	29.00 <0.00> (+1.00)
graphql-ballerina/engine_utils.bal	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
graphql-ballerina/executor_visitor.bal	92.53% <100.00%> (ø)	0.00 <0.00> (ø)
...allerina/stdlib/graphql/runtime/engine/Engine.java	92.30% <100.00%> (ø)	12.00 <0.00> (ø)

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