VaultLeaderboards v1.6

• [FIX] Added exception handling for economy providers that return null (e.g., LightEconomy v5.5.1.beta-2)
• [FIX] All economy calls now properly run asynchronously to prevent thread blocking
• [CHANGE] Balances default to 0.0 when economy provider throws exceptions

Note: LightEconomy v5.5.1.beta-2 has a bug where getBalance() returns null internally instead of 0.0 for unknown players. This violates the Vault API contract. We recommend using EssentialsX, CMI, or Treasury for stable economy integration.