Suppress IDOC if input value is blank

Hi All

We have a File to IDOC scenario.

It is a fixed length file.It contains 1 Header record with multiple line items.

if in Line item First 4 characters(field dealer) are blank then no IDOC should be created at ECC.

IDOC occurrence 0 to 1.

All the line items will be included in one IDOC.

Sample file

If file is as below IDOC should be created.This is working fine now.

Line Item:  ABCDL03000000523.8000000000010000523.8000000000010000000001MZ350004  

Requirement : if file is as below IDOC should not be created.

Line Item:       L03000000523.8000000000010000523.8000000000010000000001MZ350004  

Please help me on below questions:

1.When the occurrence is 0 to 1 can we suppress IDOC through mapping?

2.In receiver determination can we put a condition for not processing this file to ECC?

Thanks in advance!!