Fix potential memory leak when adding partybots (vmangos#3006)

Author: Gamemechanicwow

src/game/PlayerBots/PlayerBotMgr.cpp

@@ -940,6 +940,7 @@ bool ChatHandler::HandlePartyBotAddCommand(char* args)
         SendSysMessage("New party bot added.");
     else
     {
+        delete ai;
         SendSysMessage("Error spawning bot.");
         SetSentErrorMessage(true);
         return false;
@@ -979,6 +980,7 @@ bool ChatHandler::HandlePartyBotCloneCommand(char* args)
         SendSysMessage("New party bot added.");
     else
     {
+        delete ai;
         SendSysMessage("Error spawning bot.");
         SetSentErrorMessage(true);
         return false;