Guard minion skill tooltip state

[unrealdreamz]

Summary

Fixes #1787

• stops the Skills tab tooltip from crashing when a displayed minion skill has not populated minion.mainSkill
• keeps the existing main-minion-skill tooltip for fully populated minion skill state
• adds a regression fixture that exercises the malformed tooltip state from the stack trace

Root Cause

SkillsTab:AddSocketGroupTooltip treated activeSkill.minion as proof that activeSkill.minion.mainSkill.effectList[1] existed. The issue stack shows that hover/tooltips can observe a partially populated minion state where minion exists but mainSkill is nil, so the tooltip path could crash even though this is only presentation logic.

Fix

The tooltip now validates the nested minion main-skill/effect state before rendering that optional subsection. Valid minion main-skill data is still rendered exactly as before; incomplete minion state is skipped rather than taking down the Skills tab.

Validation

• busted --lua=luajit ../spec/System/TestSkills_spec.lua
  • PASS: 11 successes / 0 failures / 0 errors / 0 pending : 62.593 seconds
• git diff --check
  • PASS

Risk/Rollback

Risk is limited to the optional minion main-skill tooltip section. Fully populated minion tooltips retain the same output; incomplete state no longer crashes. Rollback is this commit only.

[LocalIdentity]

This does not fix the core issue of why the tooltip is invalid. Somehow the mainSkill list is stale when changing anything else in the build fixes the issue