try to expand column and found "Unexpected error: Value cannot be null"|Power Query|Excel Forum|My Online Training Hub

I am trying to combine different excel files which have different tab name. since every tab has some unwant rows, i would like to remove top X rows before combine them.

so I am doing the preparation work but I found a error. may I ask what is the problem seems like? i tried this code with other file, and it works for other files...

error message:

Unexpected error: Value cannot be null.
Parameter name: key
Details:
Microsoft.Mashup.Evaluator.Interface.ErrorException: Value cannot be null.
Parameter name: key ---> System.ArgumentNullException: Value cannot be null.
Parameter name: key ---> System.ArgumentNullException: Value cannot be null.
Parameter name: key

error message:

this is the code so far i have and face th error

let
Source = Folder.Files("path"),
#"Replaced Value" = Table.ReplaceValue(Source,".xlsx","",Replacer.ReplaceText,{"Name"}),
#"Removed Other Columns" = Table.SelectColumns(#"Replaced Value",{"Content", "Name"}),
#"Added Custom" = Table.AddColumn(#"Removed Other Columns", "getexcelsheet", each Excel.Workbook([Content],true)),
#"Expanded getexcelsheet" = Table.ExpandTableColumn(#"Added Custom", "getexcelsheet", {"Name", "Data", "Item", "Kind", "Hidden"}, {"Name.1", "Data", "Item", "Kind", "Hidden"})
in
#"Expanded getexcelsheet"