[Chaos Knight] Phantasm malfunctions when getting Aghanim's Scepter during cast time

[bu3ny]

When you acquire the Aghanim's Scepter during the cast time of Phantasm, the spell goes on cooldown and expends the mana, but does nothing at all besides that. It gets completely wasted.

Repro:
1. Start casting Phatasm
2. During the cast time, acquire Aghanim's Scepter (e.g. have a courier deliver it during the cast time, or get the aghs Synth buff from an allied Alchemist)

Result: When aghs is acquired during the cast time, the spell does nothing but waste mana and cooldown. Since aghs requires a target, and no target was set on cast begin, it nils, so that the spell does nothing.

Expected: When the target is nil, it should use the caster as a default target, instead of doing nothing.

Note: Weaver's Time Lapse has the same bug. Only Luna's Eclipse works properly. It defaults to Luna as the target when getting aghs during the cast time.

Edit: I also checked it for Enchant Totem and Supernova (increased its cast time to repro it), and it works fine for them as well. They default to the caster when the target is nil.

[Doofyrob]

Io tether agh talent to CK mid ult cast cancels illusion spawn

Summary:
I'm almost positive this bug is due to Io tethering at either a perfect moment OR within the cast point of CK Phantasm. In the video I provide below, CK casts ult and in doing so receives 0 illusions. At the end of his cast point for this, Io tethers to him and Io has the talent to give tether so it has an interaction issue as the casting of Phantasm no longer has a target it was cast upon. Only the initial press (which is targetting CK, but that's confused since they function changes as non-agh is single press, agh is press and select target)

Repro Steps:
From what I can tell, Io has be level 15 and have the talent "Tether Grants Scepter Bonus". Then Have CK Leveled to, at the very least 6, so he can use Phantasm. Then cast Phantasm and have Io tether CK during or at the very end of his cast point.

Result:
None of CK's illusions from Phantasm spawn and the spell goes on cooldown.

Expected Result:
2 Possible Results:
1) CK's cast point is interrupted entirely. Either cancelling the cast OR requesting a target.
2) Continue casting the ability as if CK had not received the aghanim

Also, this has the potential to be a bug with alchemist as well, granting aghanim should cause the same issue if timed properly.

[Doofyrob]

I've just tested this, it also occurs when purchasing aghanim's scepter during the cast point AND when alchemist applies the synthetic aghanim's buff during cast point. There is potential for this to be a problem with any other hero that has a change in targeting ability like phoenix (cast point is 0.01 so hard to test) and weaver (I just confirmed this in testing)

Works as intended on Luna, Riki, Sniper

*Edit: Someone also brought up the idea that it may be casting a spell that no longer exists because aghanim's may cast a new spell that replaces the old spell. but applies the cooldown still