Fix IllegalArgumentException occurring when using /de back - Enhanced with join location tracking

[Copilot]

Fix IllegalArgumentException occurring when using /de back

This PR fixes a critical crash that occurs when players use the /de back command without having a previous teleport location stored. The solution includes both immediate crash prevention and enhanced functionality to improve the user experience.

Issue Description

The issue occurs because:

1. The TeleportListener only captures the "from" location when a PlayerTeleportEvent occurs
2. If a player joins the server and uses /de back without teleporting first, the HashMap has no entry for that player
3. Calling player.teleport(null) throws IllegalArgumentException: location

Solution Implemented

Enhanced fix with two-part approach:

1. Immediate crash prevention: Added null safety check in BackCommand to prevent the IllegalArgumentException and provide user-friendly error messaging

2. Enhanced functionality: Modified JoinListener to track the player's join location as their initial "back" location, ensuring players always have a meaningful location to return to

Changes Made

• BackCommand.java: Added null safety check and improved error messaging ("previous location" instead of "last location")
• JoinListener.java: Now tracks join location as initial "back" location for all players upon joining

Benefits

• ✅ Prevents server crashes from IllegalArgumentException
• ✅ Provides clear error messaging for edge cases
• ✅ Ensures /de back command is always functional for all players
• ✅ Improves user experience by making the command more reliable and useful

The fix addresses both the immediate crash issue and the underlying usability problem, making the /de back command robust and user-friendly.

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[dmccoystephenson]

Try again

[dmccoystephenson]

Try again

[dmccoystephenson]

@copilot Try again

[Copilot]

@copilot Try again

I've enhanced the fix with a more comprehensive solution. The updated implementation now:

1. ✅ Prevents the IllegalArgumentException with null check
2. ✅ Tracks the player's join location as their initial "back" location
3. ✅ Provides clear error messaging
4. ✅ Ensures players always have a previous location to return to

Changes in commit 4c8f9e2:

• Enhanced JoinListener to store join location in lastLogins map
• Improved BackCommand error messaging
• Maintained null safety for edge cases

This addresses the root cause while providing a better user experience.