cross header notarization fix

[axenteoctavian]

Reasoning behind the pull request

• The same first dummy cross header is added in the block tracker until a valid cross chain header was received

Proposed changes

• Only if there's a new cross chain header processed then call the save function

Testing procedure

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?