Added a more explicit message in case of missing slot number

SaveExtractor/saveextractor.py

@@ -89,6 +89,8 @@ if __name__ == "__main__":
 
     if len(args) < 3 or isHelp(args):
         print(f"USAGE: python {args[0]} path/to/persistengamedata.dat slotnumber")
+        if len(args)==2:
+            print("ERROR: It seems like you forgot to specify the slot number you're importing from.")
         print("This will generate the following files:")
         print("\t- eid_savegames.lua , used by External Items Description (to be placed in EID's script folder)")
         print("\t- saveX.dat , used by Dead God Helper (to be placed in Dead God Helper data folder)")