ext file input - Error when Escape parameter is empty, fixes #7244

docs/hop-user-manual/modules/ROOT/pages/pipeline/transforms/textfileinput.adoc

@@ -124,6 +124,7 @@ Special characters (e.g. CHAR ASCII HEX01) can be set with the format $[value],
 |Escape|Specify a character or characters that are used to identify characters that should appear as-is in the field value when they might be interpreted as a control or formatting character.
 For example, if you have \ as an escape character, the text 'Not the nine o\'clock news' (where ' is the the enclosure character) gets parsed as Not the nine o'clock news instead of splitting the field value.
 Special characters (e.g. CHAR HEX01) can be set with the format $[value], e.g. $[01] or $[6F,FF,00,1F].
+The Escape character may be left empty, or set to the same character as the Enclosure. In both cases a doubled enclosure inside an enclosed field (for example "" when " is the enclosure) is treated as a single, literal enclosure character and is de-duplicated in the resulting value, following the common CSV convention (so "she said ""hi""" is read as she said "hi"). This also works when "Allow breaks in enclosed fields?" is enabled.
 |Prepend filename to headers|Enable to add the filename to each field in the file. This can help when you are joining data by making it clear which file each field comes from.
 |Header|Enable if your text file has a header row (first lines in the file). These typically determine the column names used in the transform. If you set this on a file that does not contain headers, the data values in the first row are interpreted as headers, which will likely produce unexpected results. In this case, if the field is blank, it will be named EmptyField_n, where n is the column's position in the row. Always check the field set to ensure the column names and data types have been interpreted correctly.
 |Number of header lines|Specify the number of rows encompass the header in the file.