Fix overly expensive and high level enchantments being downgraded
[bug fixed] merge level might be wrong
now the experience cost limit is 39
[bug 修复] 合并等级计算错误
现在最高经验花费将限制在39
[BUG FIXED] Enchantment level may be miscalculated when merging.
【Bug 修复】附魔等级在合并时可能被错误计算
