Mo & Krill Burrow forces quick cast even when disabled

[ibbitz]

Reproduction:

1. Buy Healing Rite
2. Face a teammate
3. Use Burrow
4. Try to self-cast Healing Rite (Press 2, then middle click)
5. Teammate will be healed instead

This feels really bad. The only way you can self-cast is by holding middle mouse while activating Healing Rite, which has gotten me killed more than once. I do not like quick casting. I want to preview who something will be cast on. But for some reason, using Burrow ignores all my settings and forces me into quick cast mode. This is not explained anywhere, and there's literally no reason it shouldn't work the same.