Update map_manager_core.sma

[lozatto]

due to lack of validation if the id is connected messages are popping up in the server log

Invalid array handle provided (0) [AMXX] Displaying debug trace (plugin "map_manager_core.amxx", version "3.3.1-959c5da") [AMXX] Run time error 10: native error (native "ArraySize") [AMXX] [0] map_manager_core.sma::get_original_num (line 692) [AMXX] [1] map_manager_core.sma::votemenu_handler (line 820)