Importing builds containg minion aura's causes crashes if their gem level is deleted

[QuickStick123]

Check version

• I'm running the latest version of Path of Building and I've verified this by checking the changelog

Check for duplicates

• I've checked for duplicate issues by using the search function of the issue tracker

Screenshots of crash/graphical issue, version and options menu

XML missing 3 fields upon import

What are your system specifications and configuration?

Not releveant for this crash.
Is on dev branch and 2.24 release.

How to reproduce the issue

1. Import this dudes profile either from poe.ninja or directly. Account: oslo663, Character: Kasza_chills
   https://poe.ninja/challenge/builds/char/oslo663/Kasza_chills
2. Delete the gem level
3. Observe Crash

This is an identical crash as #5435 #5393 #2489 but is easily caused and isn't the result of minion garbage stuff on gems.

Character build code

https://pobb.in/TtxzRkZOLCaJ

[Paliak]

This is most likely related to #4724

Changing:

PathOfBuilding/src/Classes/SkillsTab.lua

Line 668 in 3f843fb

gemInstance.level = tonumber(buf) or self.displayGroup.gemList[index].defaultLevel or self.defaultGemLevel or 20

to:

gemInstance.level = tonumber(buf) or self.displayGroup.gemList[index].defaultLevel or self:ProcessGemLevel(gemInstance.gemData) or 20

Seems to fix it but i'm not sure if that's the desired behavior.