Can't swap defender after the first was killed

[oujinlong]

Description:
Can't swap defender after the first was killed ...new defender is MISSINGNO and can't not continue to fight
Steps to reproduce:

Defender performed ACTION_SPECIAL_ATTACK
MISSINGNO attacked with special attack by SNORLAX (Defender)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_DODGE
Attacker dodged!
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Dodging special attack!
Defender performed ACTION_SPECIAL_ATTACK
MISSINGNO attacked with special attack by SNORLAX (Defender)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_DODGE
Attacker dodged!
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Defender performed ACTION_ATTACK
SNORLAX attacked by MISSINGNO (Defender)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Defender performed ACTION_ATTACK
SNORLAX attacked by MISSINGNO (Defender)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Defender performed ACTION_ATTACK
SNORLAX attacked by MISSINGNO (Defender)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Defender performed ACTION_ATTACK
SNORLAX attacked by MISSINGNO (Defender)
Defender performed ACTION_FAINT
Defender fainted!
Attacker performed ACTION_ATTACK
SNORLAX attacked by TYRANITAR (Attacker)
Defender performed ACTION_ATTACK
SNORLAX attacked by MISSINGNO (Defender)
Defender performed ACTION_VICTORY
Attacker: 74 / 141
Defender: 0 / 0

Expected behavior:
new defender is the next pokemon

Actual behavior:
new defender is the MISSINGNO

Version:
0.4.1
Thanks a lot in advance!

[RebliNk17]

I almost succeeded with fixing it, but I'm still getting an error sometimes.
I need more mitm logs to know exactly what I'm missing...

[Raventy]

Are you required to send player location after defending pokemon faints?

[Gegy]

START_GYM_BATTLE is sent when a defending pokemon faints, and the player location is sent in that.