chore: fix issue tagging script

[sundowndev-snyk]

Description

This script was throwing an error when there's no issue to create a milestone for. This PR adds a check on the ISSUES array, if it's empty, don't rewrite the array. So it will create an empty milestone for this release.

Example of failure

[karniwl]

💅

[codecov-commenter]

Codecov Report

Merging #1531 (0197053) into main (0aee331) will increase coverage by 6.71%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1531      +/-   ##
==========================================
+ Coverage   74.98%   81.69%   +6.71%     
==========================================
  Files         514      439      -75     
  Lines       19353    16023    -3330     
==========================================
- Hits        14511    13090    -1421     
+ Misses       4536     2615    -1921     
- Partials      306      318      +12     

Impacted Files	Coverage Δ
pkg/terraform/plugin_client.go	0.00% <0.00%> (-100.00%)	⬇️
pkg/remote/aws/client/s3_client_factory.go	0.00% <0.00%> (-100.00%)	⬇️
pkg/remote/aws/init.go	0.00% <0.00%> (-94.79%)	⬇️
pkg/resource/azurerm/azurerm_image.go	12.50% <0.00%> (-87.50%)	⬇️
pkg/resource/azurerm/azurerm_resource_group.go	12.50% <0.00%> (-87.50%)	⬇️
pkg/resource/google/google_compute_address.go	14.28% <0.00%> (-85.72%)	⬇️
...g/resource/google/google_compute_global_address.go	14.28% <0.00%> (-85.72%)	⬇️
...ce/google/google_compute_instance_group_manager.go	14.28% <0.00%> (-85.72%)	⬇️
pkg/remote/azurerm/init.go	0.00% <0.00%> (-84.22%)	⬇️
pkg/resource/aws/aws_lb.go	16.66% <0.00%> (-83.34%)	⬇️
... and 176 more