AI Ugin's Mastery second ability badly

**Describe the bug**
When the AI has manifested cards + Ugin's Mastery on the battlefield and attacks such that Ugin's Mastery's second ability triggers, AI always selects the first morph card from the left. If the leftmost card is an instant/sorcery, this results in the card being revealed to all players and not flipping because it's not a permanent, wasting the trigger.

**To Reproduce**
Steps to reproduce the behavior:
1. Create a game where the AI has an Ugin's Mastery on the battlefield (can be achieved using the Eldrazi Unbound commander precon)
2. Let the AI cast colourless spells, manifesting cards from their library
3. When the AI attacks with total power 6 or greater, they will choose the leftmost card. Even if there are manifested creatures / permanents.

**Expected behavior**
A human player would refuse to attempt to flip an instant/sorcery as Ugin's Nexus is a may ability. If there is a creature manifested, then a human will likely always choose the creature. If there are any other permanents manifested, the player may choose to flip them depending on the game state.

**Screenshots**
AI triggering Ugin's Mastery and selecting the leftmost card

Manifested cards in graveyard post board wipe (minus cicada)

In the case above, Bane of Bala Ged would be the choice to flip. Otherwise, Forsaken Monument is a fantastic choice.

**Desktop (please complete the following information):**
- OS: Windows 10
- Version: forge-1.6.60