BattleTest and EventTest can't start

[rev2nym]

BattleTest and EventTest can't be started by RPGM MV editor ver 1.6.1.

[krmbn0576]

Thanks! Now corescript is based on RMMV 1.4.1, so Utils.isOptionValid() is still old. We'll merge 1.6.1 soon later!

[rev2nym]

Thank you.

Please keep in mind that official 1.6.1 method is a bit inappropriate.

• It returns 0/1. Expected return value is bool type.
• It is very hard to read because the line is so long.