How to add merge and check if column was not deleted|Power Query|Excel Forum|My Online Training Hub

Hi Guys,

i have query like:

let
Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Key", Int64.Type}, {"Key2", Int64.Type}, {"Col2", type text}, {"Col3", type text}}),
#"Merged Queries" = Table.NestedJoin(#"Changed Type", {"Key", "Key2"}, Table13, {"Key", "Key2"}, "Table13", JoinKind.Inner),
#"Removed Columns" = Table.RemoveColumns(#"Merged Queries",{"Table13"}),
#"Unpivoted Columns" = Table.UnpivotOtherColumns(#"Removed Columns", {"Key", "Key2"}, "Attribute", "Value"),
#"Removed Columns1" = Table.RemoveColumns(#"Unpivoted Columns",{"Attribute"})
in
#"Removed Columns1"

And now in step #"Merged Queries"  i am merging table1 with Table13 using inner join. 
Where is the issue that Key2 in Table13 can be removed and i will get error:

Expression.Error: The column 'Key2' of the table wasn't found.
Details:
Key2

What i want to do is add If statetement or try statement and if Key2 was removed just use inner join for "Key" field. 
(use one column not 2 within inner join). 

How can i do this? 
Best,
Jacek