Fixed index error

db.json

@@ -1 +1 @@
-{"_default": {"1": {"Serial Number": "123", "Brand": "d", "Grade": "7", "Name": "jb"}, "2": {"Serial Number": "1", "Brand": "2", "Grade": "3", "Name": "4"}}}
+{"_default": {}}

main.py

@@ -122,7 +122,7 @@ def main():
             )
             window["table"].update(format_table(result))
 
-        elif event == "table":
+        elif event == "table" and values["table"]:
             row=window["table"].get()[values["table"][0]]
             window["Serial Number"].update(row[0])
             window["Brand"].update(row[1])