Fix bug where users could rob negative balances

Author: TechnoVisionDev

src/main/java/technobot/handlers/economy/EconomyHandler.java

@@ -105,6 +105,7 @@ public EconomyReply rob(long userID, long targetID) {
 
         // Calculate mount stolen (success probability * their cash)
         long amountStolen = (long) ((1 - failChance) * targetCash);
+        if (amountStolen < 0) amountStolen = 0;
 
         // Attempt robbery
         setTimeout(userID, TIMEOUT_TYPE.ROB);