Using Give Command crashes Server

[rayrobdod]

problem

Description:

When a unit attempts to use the Give command, (transfer a rescued unit from itself to another unit), the server crashes.

SPECS:

CPU: Intel Core i5 @2.5GHz (64 bit)

GPU: Intel HD Graphics 620

RAM: ~8GB

OS: Windows 10

JRE Ver: Java(TM) SE Runtime Environment (build 9.0.4+11)

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Expected Behavior:

The rescued unit is transferred from the giver to the givee from the perspective of both clients.

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Actual Behavior:

The server crashes

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Steps to Reproduce:

With three units, Unit B being able to be rescued by both units A and C.

1. Blue turn one, have unit A rescue unit B, then end turn.
2. Red turn one, end turn
3. Blue turn two, have unit A Give to unit C.

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Examples:

This specific error_log_sever is from f66572a, although anything newer than v1.5 inclusive gives a similar error log.

java.lang.IllegalStateException: rescuedUnit == null
	at net.fe.unit.Unit.give(Unit.java:302)
	at net.fe.network.command.TakeCommand.applyServer(TakeCommand.java:31)
	at net.fe.overworldStage.OverworldStage.processCommands(OverworldStage.java:366)
	at net.fe.overworldStage.OverworldStage.executeMessage(OverworldStage.java:266)
	at net.fe.overworldStage.OverworldStage.beginStep(OverworldStage.java:259)
	at net.fe.network.FEServer.loop(FEServer.java:116)
	at net.fe.network.serverui.FEServerFrame.lambda$serverStart$0(FEServerFrame.java:57)
	at java.base/java.lang.Thread.run(Unknown Source)

Attempting to give on v1.4 also crashes the server, but with a completely different error_log_sever.

java.lang.IllegalArgumentException: Unkown command: GIVE
	at net.fe.overworldStage.OverworldStage.processCommands(OverworldStage.java:448)
	at net.fe.overworldStage.OverworldStage.beginStep(OverworldStage.java:263)
	at net.fe.network.FEServer.loop(FEServer.java:347)
	at net.fe.network.FEServer$4$2.run(FEServer.java:263)

In v1.3, the server doesn't crash, but the rescued unit isn't transferred in the opponent's game leading to a desynch and, eventually, a client crash via null dereference.