Fix: ArgumentNullException on output-only Terraform plans

This release is a bug-fix-only update. It fixes a crash (ArgumentNullException) that occurred when processing Terraform plans where the resource_changes field is absent or explicitly null — a situation that arises with output-only plans (plans that change only outputs, with no infrastructure resource changes).

🐛 Bug fixes

• Fixed crash on output-only plans: tfplan2md previously threw ArgumentNull_Generic Arg_ParamName_Name, source when the input plan JSON had no resource_changes key (or "resource_changes": null). The tool now treats a missing or null resource_changes as an empty list and produces a valid report showing only the output changes.
• Null-safe action handling: Additional null guards added for Change.Actions and OutputChange.Actions to protect against similarly missing fields in unusual plan formats.

Affected scenarios

• Terraform plans generated on workspaces with only output block changes and no resource add/change/destroy operations
• Plans produced by Terraform 1.13.x (confirmed with user-reported plan from Terraform 1.13.3)
• Any plan where "resource_changes" is omitted or set to null in the JSON

🔗 Commits

• 2de4452 fix: handle null resource_changes/actions in tfplan.json gracefully