Added duplicate Ai check.

servermanager.py

@@ -222,9 +222,12 @@ def server_command_builder(
     if not hwrap:
         command.append(" --nohwrap")
     if ai_slots:
+        added_ais = []
         for ai in ai_slots:
             if ai[0] not in available_nations[str(era)]:
                 return "ERROR_INVALID_NATION"
+            if ai[0] in added_ais:
+                return "ERROR_DUPLICATE_AI"
             match ai[1]:
                 case 1:
                     command.append(" --easyai " + str(ai[0]))
@@ -240,6 +243,7 @@ def server_command_builder(
                     command.append(" --impai " + str(ai[0]))
                 case _:
                     return "ERROR_INVALID_AI"
+            added_ais.append(ai[0])
 
     return "".join(command)