Incorrect/Inproper input to loading a save file will crash entire program

[nus-pe-bot]

Steps to recreate bug:

1. Start program using java -jar
2. Select input option 2 (Load Game option)
3. User may enter "2" or any non-fully integer input (e.g "d", 12s", "2.0" etc)
4. The program will then show just show a new line
5. Pressing enter again will cause the entire program to crash

The program in this scenario does not handle incorrect input correctly, and does not fail gracefully, it also affects when saving the game and choosing a slot to save in. See images attached for more information

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_{[original: nus-cs2113-AY2425S2/pe-interim#1127] [original labels: type.FunctionalityBug severity.Medium]}

[TiangSoonYong]

Team's Response

This is a duplicated bug report regarding unhandled exception of invalid input.

Duplicate status (if any):

Duplicate of #547