_endGameFromInvite fixes

#### What's this PR do?
Fixes:
* Players not receiving the "your game has ended" message
* Incorrectly ending games where the player being pulled out of a group never actually joined the ended game

#### Where should the reviewer start?
* `players[playerIdx]` on line 1355 fixes the first issue.
* The `skipGame` logic fixes the second issue.

#### How should this be manually tested?
I manually tested the following scenarios:
* **Scenario 1**
  * Creating a game with player A, B1, B2, and B3
  * B1 joins. A starts the game
  * B2 creates a new game
  * Verified A and B1 are NOT pulled out of their game
* **Scenario 2**
  * Creating a game with player A, B1, B2, and B3
  * B1 and B2 join. A starts the game
  * B3 creates a new game and invites B1
  * Verified A and B2 get the "your game has ended" message
 
#### Any background context?
This should resolve at least some of the 404 errors the app's been throwing.