This is a problem when selection a range with an inputbox. Excel returns an error before the range is returned, and it carries this error on when you press cancel.
You should therefore actively handle this error. If you don’t want anything to happen when you press cancel, you can just use the code like this:
Sub SetRange()
Dim selectRange As Range
On Error Resume Next
Set selectRange = Application.InputBox("Select your range", "Hello", , , , , , 8)
Err.Clear
On Error GoTo 0
End Sub