Help! E-file I-131 problems

I tried to E-file I-131 form, and received the below warning which made me so nervous.

WARNING: It is suggested that you provide your Middle Initial. Failure to do so may result in your application or petition being delayed or denied.

I do not have a middle name and the Middle Initial area is optional (not required), so I left it blank. Several steps later, when I tried to certify the I-131 form, it appears the following message:

Fix Errors

You have attempted to certify an application that does not have all of the suggested fields completed. It is recommended that all suggested fields be completed in order to expedite the application process.

Please click the Fix Errors button below and you will be taken the the Form Checklist for a listing of the forms that have errors. Any form that has incomplete suggested fields will be in the alert section at the top of the page. Select the link for that form from the form checklist to fix the suggested fields for that form.

To continue with certification process, select the Certify Form button. Please note that forms with suggested fields may delay processing your application.

I filled all the required area. Should I ignore the warning? I tried to put "Not Applicable" on but it allows only one letter. What should I do? No Middle initial = petition delayed or denied?

Anyone has E-file I-131 experience? Have you met this problem? Thank you very much for the input and suggestions. My I-485 has been pending for almost 4 years, It is really frustrated to have to apply the AP and EAD without knowing when can be freed. Thanks for all the kind reply.