Error while processing files only with header line

hello,

while processing files only with one Header line (SFTP Adatapter -> Java Mapping -> Message Mapping -> Idoc) the idoc adapter is throwing
following error message:

Split mapping created no messages, cannot proceed. Review your mapping setup: splitting to 0 messages is not allowed.

any ideas? i think we have to configure the SFTP Receiver Adapter but the file isnt empty because of the Header line. is there any way without creating own module? thanks