Battle with less than 3 pokemon (kinda QOL)

[mrrevillo0815]

Describe the bug
When starting to battle someone while having only one pokmon, (recreating the rivals battle in the beginning of the games) there is no error message showing, and the battle is not being cancelled automatically (as would be expected)

To Reproduce
Pick starter, try to battle someone

Expected behavior
Cancel the battle and show an error-msg stating that you don't have enough Pokemon yet